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| United States Patent |
5,731,263
|
|
Totsuka
, et al.
|
March 24, 1998
|
Image forming method
Abstract
A heat sensitive ink sheet has a heat sensitive ink layer which is formed
of a heat sensitive ink material comprising colored pigment and
thermoplastic resin such as amorphous organic polymer. An image receiving
sheet having a support sheet and an image receiving layer thereon, the
support sheet of the image receiving sheet being a porous sheet made of
plastics which have fine pores therein. An image forming method is
conducted by using the heat sensitive ink sheet and an image receiving
sheet by area gradation by the use of a thermal head or laser beam.
| Inventors:
|
Totsuka; Mikio (Shizuoka, JP);
Tanaka; Toshiharu (Shizuoka, JP);
Takahashi; Yonosuke (Shizuoka, JP);
Yoshinari; Shinichi (Shizuoka, JP)
|
| Assignee:
|
Fuji Photo Film Co., Ltd. (Kanagawa, JP)
|
| Appl. No.:
|
637526 |
| Filed:
|
April 25, 1996 |
Foreign Application Priority Data
| Apr 25, 1995[JP] | 7-124452 |
| Sep 01, 1995[JP] | 7-248382 |
| Current U.S. Class: |
503/227; 428/304.4; 428/913; 428/914; 430/256; 430/326 |
| Intern'l Class: |
B41M 005/035; B41M 005/38 |
| Field of Search: |
8/471
428/195,304.4,913,914
503/227
|
References Cited
U.S. Patent Documents
| 5244861 | Sep., 1993 | Campbell et al. | 503/227.
|
Primary Examiner: Hess; Bruce H.
Attorney, Agent or Firm: Birch, Stewart, Kolasch & Birch, LLP
Claims
What is claimed is:
1. An image forming method which comprises the steps of:
superposing a heat sensitive ink sheet having a base sheet and a heat
sensitive ink layer thereon on an image receiving sheet having a support
sheet and an image receiving layer thereon in such a manner that the heat
sensitive ink layer is in contact with the image receiving layer, said
heat sensitive ink layer of the heat sensitive ink sheet having a
thickness of 0.2 to 1.0 .mu.m and being formed of a heat sensitive ink
material which comprises 30 to 70 weight % of colored pigment and 25 to 65
weight % of amorphous organic polymer having a softening point of
40.degree. to 150.degree. C., and said support sheet of the image
receiving sheet comprising a porous sheet made of plastics;
placing imagewise a thermal head on the base sheet of the heat sensitive
ink sheet to form an image of the ink material with area gradation on the
image receiving layer; and
separating the base sheet of the heat sensitive ink sheet from the image
receiving sheet so that the image of the ink material can be retained on
the image receiving layer, said image of the ink material on the image
receiving layer having an optical reflection density of at least 1.0.
2. The image forming method as defined in claim 1, which further contains
the steps of:
superposing the image receiving sheet having the image on a white paper
sheet in such a manner that the image of the ink material is in contact
with a surface of the white paper sheet; and
separating the image receiving sheet from the white paper sheet, keeping
the image of the ink material on the white paper sheet, said image of the
ink material on the white paper sheet having an optical reflection density
of at least 1.0.
3. The image forming method as defined in claim 1, wherein at least 70
weight % of the colored pigment has a particle size of 0.1 to 1.0 .mu.m.
4. The image forming method as defined in claim 1, wherein the support
sheet of the image receiving sheet is made of at least one material
selected from the group consisting of polyester, polyamide, polycarbonate,
polyethersulfone, polyimide, polyolefin, polyvinyl chloride, polyurethane,
polyvinylidene chloride, polyacrylate and cellulose acetate.
5. The image forming method as defined in claim 1, wherein the support
sheet of the image receiving sheet has a thickness of 50 to 250 .mu.m.
6. The image forming method as defined in claim 1, wherein the support
sheet of the image receiving sheet is a porous sheet which is sandwiched
between a backing layer and an anti-curling layer.
7. The image forming method as defined in claim 1, wherein the image
receiving layer of the image receiving sheet comprises two layers.
8. A composite in which comprises an image receiving sheet having a support
sheet and an image receiving layer thereon and a heat sensitive ink sheet
having a base sheet and a heat sensitive ink layer thereon which are
superposed in such a manner that the heat sensitive ink layer is in
contact with the image receiving layer,
said heat sensitive ink layer of the heat sensitive ink sheet having a
thickness of 0.2 to 1.0 .mu.m and being formed of a heat sensitive ink
material comprising 30 to 70 weight % of colored pigment and 25 to 65
weight % of amorphous organic polymer having a softening point of
40.degree. to 150.degree. C., and said support sheet of the image
receiving sheet comprising a porous sheet made of plastics.
9. An image forming method which comprises the steps of:
superposing a heat sensitive ink sheet having a base sheet and a heat
sensitive ink layer thereon on an image receiving sheet having a support
sheet and an image receiving layer thereon in such a manner that the heat
sensitive ink layer is in contact with the image receiving layer, said
heat sensitive ink layer of the heat sensitive ink sheet being formed of a
heat sensitive ink material which comprises colored pigment and
thermoplastic resin and said support sheet of the image receiving sheet
comprising a porous sheet made of plastics;
irradiating a laser beam modulated by digital signals on the heat sensitive
ink layer through the base sheet of the heat sensitive ink sheet to form
an image of the ink material on the image receiving layer; and
separating the base sheet of the heat sensitive ink sheet from the image
receiving sheet so that the image of the ink material can be retained on
the image receiving sheet.
10. The image forming method as defined in claim 9, wherein the formation
of the image of the ink material on the image receiving sheet is done by
ablation of the image from the base support of the heat sensitive ink
sheet.
11. The image forming method as defined in claim 9, wherein further
contains the steps of:
superposing the image receiving sheet having the image on a white paper
sheet in such a manner that the image of the ink material is in contact
with a surface of the white paper sheet; and
separating the image receiving sheet from the white paper sheet, keeping
the image of the ink material on the white paper sheet.
12. The image forming method as defined in claim 9, wherein the support
sheet of the image receiving sheet is made of at least one material
selected from the group consisting of polyester, polyamide, polycarbonate,
polyethersulfone, polyimide, polyolefin, polyvinyl chloride, polyurethane,
polyvinylidene chloride, polyacrylate and cellulose acetate.
13. The image forming method as defined in claim 9, said support sheet of
the image receiving sheet has a thickness of 50 to 300 .mu.m.
14. The image forming method as defined in claim 9, wherein the support
sheet of the image receiving sheet is a porous sheet which is sandwiched
between a backing layer and an anti-curling layer.
15. The image forming method as defined in claim 9, wherein said heat
sensitive ink layer of the heat sensitive ink sheet is formed of a heat
sensitive ink material comprising 30 to 70 weight % of colored pigment and
30 to 70 weight % of thermoplastic resin.
16. The image forming method as defined in claim 9, wherein said
thermoplastic resin is amorphous organic polymer having a softening point
of 40 to 150.degree. C.
17. The image forming method as defined in claim 9, wherein said heat
sensitive ink layer of the heat sensitive ink sheet has a thickness of 0.2
to 1.5 .mu.m.
18. The image forming method as defined in claim 9, wherein the heat
sensitive ink sheet further has a light-heat conversion layer between the
base sheet and the heat sensitive ink layer.
19. The image forming method as defined in claim 9, wherein in the step of
superposing a heat sensitive ink sheet on an image receiving sheet, the
superposing is conducted in the application of pressure of 1 to 30
kg/cm.sup.2.
Description
FIELD OF THE INVENTION
This invention relates to an image forming method and a composite of a heat
sensitive ink sheet and an image receiving sheet favorably employable for
the method. In more detail, the invention relates to an image forming
method for forming a multicolor image on an image receiving sheet by area
gradation using a thermal head or laser beam.
BACKGROUND OF THE INVENTION
Heretofore, there have been known two methods for thermal transfer
recording for the preparation of a multicolor image which utilize a
thermal head printer, that is, a sublimation dye transfer recording method
and a fused ink transfer recording method.
The sublimation dye transfer recording method comprises the steps of
superposing on an image receiving sheet an image transfer sheet which is
composed of a support and an image transfer layer comprising a sublimation
ink and a binder and imagewise heating the support of the transfer sheet
to sublimate the sublimation ink to form an image on the image receiving
sheet. A multicolor image can be prepared using a number of color transfer
sheets such as a yellow transfer sheet, a magenta transfer sheet, and a
cyan transfer sheet.
The sublimation dye transfer recording method, however, has the following
drawbacks:
1) The gradation of image is mainly formed of variation of the sublimated
dye concentration, which is varied by controlling the amount of
sublimation of the dye. Such gradation is appropriate for the preparation
of a photographic image, but is inappropriate for the preparation of a
color proof which is utilized in the field of printing and whose gradation
is formed of dots, lines, or the like, that is, area gradation.
2) The image formed of sublimated dye has poor edge sharpness, and a fine
line shows thinner density on its solid portion than a thick line. Such
tendency causes serious problem in the quality of character image.
3) The image of sublimated dye is poor in endurance. Such image cannot be
used in the fields which require multicolor images resistant to heat and
light.
4) The sublimation dye transfer recording shows sensitivity lower than the
fused ink transfer recording. Such low sensitive recording method is not
preferably employable in a high speed recording method utilizing a high
resolution thermal head, of which development is expected in the future.
5) The recording material for the sublimation dye transfer recording is
expensive, as compared with the recording material for the fused ink
transfer recording.
The fused ink transfer recording method comprises the steps of superposing
on an image receiving sheet an image transfer sheet having support and a
thermal fusible transfer layer which comprises a coloring material (e.g.,
pigment or dye) and imagewise heating the support of the transfer sheet to
portionwise fuse the transfer layer to form and transfer an image onto the
image receiving sheet. A multicolor image also can be prepared using a
number of color transfer sheets.
The fused ink transfer recording method is advantageous in the sensitivity,
cost, and endurance of the formed image, as compared with the sublimation
dye transfer recording method. It, however, has the following drawbacks:
The color image prepared by the fused ink transfer recording method is poor
in its quality, as compared with the sublimation dye transfer recording
method. This is because the fused ink transfer recording utilizes not
gradation recording but binary (i.e., two valued) recording. Therefore,
there have been reported a number of improvements on the fusible ink layer
of the fused ink transfer recording method for modifying the binary
recording to give gradation recording so that a color image having
multi-gradation is preparedly the fused ink transfer recording method. The
basic concept of the heretofore reported improvement resides in
portionwise (or locally) controlling the amount of the ink to be
transferred onto the image receiving sheet. In more detail, the mechanism
of transfer of the ink in the fused ink transfer recording method is as
follows; under heating by the thermal head, the viscosity of the ink layer
at the site in contact with the thermal head lowers and the ink layer
tends to adhere to the image receiving sheet, whereby the transfer of the
ink takes place. Therefore, the amount of the transferred ink can be
controlled by varying degree of elevation of temperature on the thermal
head so that the cohesive failure in the ink layer is controlled and the
gamma characteristic of the transferred image is varied. Thus, the optical
density of the transferred ink image is portionwise varied, and
accordingly, an ink image having gradation is formed. However, the optical
density of a fine line produced by the modified fused ink transfer
recording is inferior to that produced by the sublimation dye transfer
recording method. Moreover, the optical density of a fine line produced by
the modified fused ink transfer recording method is not satisfactory.
Further, the fused ink transfer recording method has other disadvantageous
features such as low resolution and poor fixation of the transferred ink
image. This is because the ink layer generally uses crystalline wax having
a low melting point as the binder, and the wax tends to spread on the
receiving sheet in the course of transferring under heating. Furthermore,
the crystalline wax scarcely gives a transparent image due to light
scattering on the crystalline phase. The difficulty in giving a
transparent image causes serious problems in the preparation of a
multicolor image which is formed by superposing a yellow image, a magenta
image, and a cyan image. The requirement to the transparency of the formed
image restricts the amount of a pigment to be incorporated into the ink
layer. For instance, Japanese Patent Publication No. 63(1988)-65029
describes that the pigment (i.e., coloring material) should be
incorporated in the ink layer in an amount of not more than 20 weight %
based on the total amount of the ink layer. If an excessive amount of the
pigment is employed, the transparency of the transferred ink image is made
dissatisfactory.
Improvements of reproduction of a multicolor image in the fused ink
transfer recording have been studied and proposed, so far. For instance,
Japanese Patent Provisional Publication No. 61(1986)-244592(=Japanese
Patent Publication No. 5(1993)-13072) describes a heat sensitive recording
material which has a heat sensitive layer comprising at least 65 weight %
of an amorphous polymer, a releasing agent, and a coloring material (dye
or pigment) which can reproduce a color image having continuous gradation
with improved transparency and fixation strength. The publication
indicates that the amorphous polymer in an amount of 65 weight % gives a
heat sensitive ink layer of extremely poor transparency and therefore
cannot reproduce a satisfactory color image, and at least 70 weight % of
the amorphous polymer is required to give a sufficiently transparent ink
layer. Further, the amount of the coloring material is required to be not
more than 30 weight % to obtain the sufficiently transparent ink layer. As
for the thickness of the heat-sensitive ink layer, it is described that
0.5 .mu.m to 50 .mu.m, specifically 1 .mu.m to 20 .mu.m, is preferred to
obtain practical density or strength of an image. In the working examples,
the thickness of the ink layer is approximately 3 .mu.m which is similar
to that of the conventional ink layer using wax binder. Furthermore, the
publication indicates that the heat sensitive recording material can also
utilize binary recording and multi-valued recording (i.e., image recording
method utilizing multi-dots having area different from one another; VDS
(Variable Dot System)).
The study of the inventors has clarified that recording by the continuous
gradation using the heat sensitive recording material of the publication
does not give an image having satisfactory continuity and stability of
density. Further, the binary or multi-valued recording using the heat
sensitive recording material does not give an image having satisfactory
continuity of density, transparency (especially transparency of multicolor
image) and sharpness in the edge portion.
In contrast, it is known that a thermal transfer recording method can
prepare a multicolor image having multi-gradation by means of the
multi-valued recording which utilizes area gradation. Further, it is also
known that a heat sensitive ink sheet which can be used in the
multi-valued recording utilizing area gradation, preferably have the
following characteristics:
(1) Each color image (i.e., cyan image, magenta image or yellow image) of
the multicolor image for color proofing should have a reflection density
of at least 1.0, preferably not less than 1.2, and especially not less
than 1.4, and a black image preferably has a reflection density of not
less than 1.5. Thus, it is desired that the heat sensitive ink sheet has
the above reflection densities.
(2) An image which is produced by area gradation is satisfactory.
(3) An image can be produced in the form of dots, and the formed line or
point has high sharpness in the edge.
(4) An ink layer (image) transferred has high transparency.
(5) An ink layer has high sensitivity.
(6) An image transferred onto a white paper (e.g., coated paper) should be
analogous to a printed image in tone and surface gloss.
As for the thermal head printer, the technology has been very rapidly
developed. Recently, the thermal head is improved to give a color image
with an increased resolution and multi-gradation which is produced by area
gradation. The area gradation means gradation produced not by variation of
optical density in the ink area but by size of ink spots or lines per unit
area. Such technology is described in Japanese Patent Provisional
Publications No. 4(1992)-19163 and No. 5(1993)-155057 (for divided
sub-scanning system) and the preprint of Annual Meeting of Society of
Electrography (Jul. 6, 1992)(for heat concentrated system).
The image receiving sheet (materials to be transferred) in the transfer
image forming method, usually has a structure wherein an adhesive layer
(image receiving layer) containing an organic polymer is provided on a
support, in order to prevent occurrence of uneven transfer and
transferring error of dot which are originated from evenness or
ink-receivable properties of the surface of the image receiving layer
(U.S. Pat. Nos. 4,482,625, 4,766,053 and 4,933,258). As materials for the
image receiving sheet, a paper, a synthetic paper and polymer films are
usually employed. Especially, polyethylene terephthalate film is
advantageously employed due to excellent heat resistance property, even
surface and low cost.
As a transfer image forming method using the heat sensitive ink sheet,
recently a method using a laser beam (i.e., digital image forming method)
has been developed. The method comprises the steps of: superposing the
heat sensitive ink layer of the heat sensitive ink sheet on an image
receiving sheet, and applying a laser beam modulated by digital signal
onto the heat sensitive ink layer through the support of the heat
sensitive ink sheet to form and transfer an image of the heat sensitive
ink layer onto the image receiving sheet (the image can be further
retransferred onto other sheet). In the method, the heat sensitive ink
sheet generally has a light-heat conversion layer provided between the ink
layer and the support to efficiently convert light energy of laser beam
into heat energy. The light-heat conversion layer is a thin layer made of
carbon black or metal. Further, a method for locally peeling the ink layer
to transfer the peeled ink layer onto the image receiving sheet (i.e.,
ablation method), which does not fuse the layer in the transferring
procedure, is disclosed in Japanese Patent Provisional Publication No.
6(1994)-219052. The method is utilized in order to enhance image quality
such as evenness of reflection density of the image or sharpness in edges
of the image.
The image receiving sheet (materials to be transferred) in the transfer
image forming method using a laser beam mentioned above, usually has a
structure wherein an adhesive layer (image receiving layer) containing an
organic polymer is provided on a support, in order to prevent occurrence
of uneven transfer and transferring error of dot which are originated from
evenness or ink-receivable properties of the surface of the image
receiving layer, as described in the Publication (No. 6(1994)-219052).
Further, as materials for the image receiving sheet, a paper, a synthetic
paper and a polymer films (e.g., polyethylene terephthalate,
polycarbonate, polyethylene, polyvinyl chloride, polyvinylidene chloride,
polystyrene and styrene/acrylonitrile copolymer) are usually employed.
Especially, the Publication describes a biaxially oriented polyethylene
terephthalate film is preferably employable due to good dimensional
resistance to moisture or heat.
SUMMARY OF THE INVENTION
The known image forming methods using a thermal head do not satisfactorily
give an image which has dots having preferable size and shape and good
reproduction of gradation and which is well analogous to a printed image.
The copending application discloses that a thin layer
heat-sticking-peeling method (i.e., method using a heat sensitive sheet
provided with a thin ink layer containing pigment in high content) is
advantageous for giving an image having excellent characteristics
described above (see U.S. application Ser. No. 08/327,409 or EP
Application No. 94116673.8). The use of the above heat sensitive ink sheet
gives a high quality color or monochrome image with multi-gradation which
is produced by area gradation, and therefore the ink sheet is useful for
not only the usual image forming method but also preparation of color
proof in the printing field and block copy. Further, the pigments
contained in the ink sheet have good durability and therefore the ink
sheet is also useful for preparation of elements employed in the fields of
the recordable or recorded card and outdoor or meter display.
In order to further improve quality of an image with multi-gradation which
is produced by area gradation, desired are the improvements of the image
receiving sheet as well as the heat sensitive ink sheet. In more detail,
quality of the resultant image varies depending upon the transferring
property (i.e., adhesion between the ink layer and the image receiving
layer).
In the above thin layer heat-sticking-peeling method, various image defects
(e.g., nonuniformity of concentration and occurrence of line) are almost
produced depending on the properties of material or surface of the image
receiving sheet. The image defects reduce the quality of the final image
which is formed on a white paper sheet. Otherwise, in a heat transferring
procedure using a thermal transfer printer, the image receiving sheet
occasionally lodges (stops running) in the thermal transfer printer during
running of the sheet. Further, the image receiving sheet also tends to
bring about occurrence of other trouble (e.g., trouble on feeding the
sheet) during running of the sheet.
An object of the present invention is to provide an image forming method
which is improved in transfer properties in a thermal transfer recording
method using a heat sensitive ink layer of a heat sensitive ink sheet
satisfying the characteristics described above (1) to (6), and which is
capable of forming a transferred image by multi-gradation.
Another object of the invention is to provide an image forming method
capable of giving an image which has dots having preferable size and shape
(i.e., near to predetermined size and shape) and good reproduction of
gradation and which is well analogous to a printed image.
A further object of the invention is to provide a composite of a heat
sensitive ink sheet and an image receiving sheet which is suitable for the
above image forming method.
A still further object of the invention is to provide an image forming
method using a laser beam which is capable of recording uniformly an image
in high sensitivity and giving an image of high quality in which image
defect is reduced.
The inventors have studied to obtain an image of high quality in which
image defect is reduced in the thin layer heat-sticking-peeling method. As
a result, the inventors have found that the satisfactory image can be
obtained by the use of a sheet made of plastics which have fine pores
therein as a support sheet of the image receiving sheet, in the thin layer
heat-sticking-peeling method. In more detail, the use of the plastic sheet
having fine pores gives cushion property to the image receiving layer of
the image receiving sheet, and therefore pressing by the thermal head in
the transfer procedure brings about high and even adhesion between the ink
layer and the image receiving layer. Hence, the composite (of an image
receiving sheet and heat sensitive ink sheet) is improved in ability
following up heat information given by the thermal head, which results in
reduction of image defects. Further, the use of the plastic sheet having
fine pores also softness the image receiving sheet per se, and therefore
scarcely brings about occurrence of trouble during running of the sheet in
a thermal transfer printer. Furthermore, when a relatively large dust is
incorporated between the heat sensitive ink sheet and the image receiving
sheet in the procedure that the heat sensitive ink sheet is superposed on
the image receiving sheet, the soft sheet almost absorbs the deformation
to be formed between the sheets in the procedure to reduce defects of the
resultant image.
Moreover, the present inventors have found that the plastic sheet having
fine pores is useful in an image forming method using a laser beam. When a
laser beam is irradiated on the heat sensitive ink layer of the composite
(heat sensitive ink sheet and image receiving sheet) through a back of the
image receiving sheet, the heat sensitive ink layer shows high sensibility
because the image receiving sheet of the composite has low heat
conductivity due to fine pores. In more detail, thermal energy given on
the heat sensitive ink sheet scarcely shows loss by heat diffusion due to
low heat conductivity of the plastic sheet (support sheet), and therefore
a temperature in the irradiated area at the interface between the heat
sensitive ink layer and image receiving layer increases compared with in
the case of the use of a conventional image receiving sheet, whereby the
heat sensitive ink layer is rendered highly sensitive. Furthermore,
advantages given in the image forming method using thermal head (e.g.,
reduction of image defects by enhanced ability following up heat
information of a laser beam and little occurrence of trouble during
running of the sheet in a printer) can be also obtained in the case of
using a laser beam.
There is provided by the present invention an image forming method which
comprises the steps of:
superposing a heat sensitive ink sheet having a base sheet and a heat
sensitive ink layer thereon on an image receiving sheet having a support
sheet and an image receiving layer thereon in such a manner that the heat
sensitive ink layer is in contact with the image receiving layer, said
heat sensitive ink layer of the heat sensitive ink sheet having a
thickness of 0.2 to 1.0 .mu.m and being formed of a heat sensitive ink
material which comprises 30 to 70 weight % of colored pigment and 25 to 65
weight % of amorphous organic polymer having a softening point of
40.degree. to 150.degree. C., and said support sheet of the image
receiving sheet comprising a porous sheet made of plastics;
placing imagewise a thermal head on the base sheet of the heat sensitive
ink sheet to form an image of the ink material with area gradation on the
image receiving layer; and
separating the base sheet of the heat sensitive ink sheet from the image
receiving sheet so that the image of the ink material can be retained on
the image receiving layer, said image of the ink material on the image
receiving layer having an optical reflection density of at least 1.0.
The preferred embodiments of the above-mentioned image forming method are
as follows:
1) The image forming method which further contains the steps of:
superposing the image receiving sheet having the image on a white paper
sheet in such a manner that the image of the ink material is in contact
with a surface of the white paper sheet; and
separating the image receiving sheet from the white paper sheet, keeping
the image of the ink material on the white paper sheet preferably said
image of the ink material on the white paper sheet having an optical
reflection density of at least 1.0.
2) The image forming method wherein at least 70 weight % of the colored
pigment has a particle size of 0.1 to 1.0 .mu.m.
3) The image forming method wherein the support sheet of the image
receiving sheet is made of at least one material selected from the group
consisting of polyester, polyamide, polycarbonate, polyethersulfone,
polyimide, polyolefin, polyvinyl chloride, polyurethane, polyvinylidene
chloride, polyacrylate and cellulose acetate.
4) The image forming method wherein the support sheet of the image
receiving sheet has a thickness of 50 to 250 .mu.m.
5) The image forming method wherein the support sheet of the image
receiving sheet is a porous sheet which is sandwiched between a backing
layer and an anti-curling layer, the image receiving layer being not
provided on the backing layer, and the image receiving layer being
provided on the curling layer.
6) The image forming method wherein the image receiving layer of the image
receiving sheet comprises at least two layers (preferably comprises a
first image receiving layer and a second image receiving layer).
7) The image forming method wherein the heat sensitive ink contains an
amide compound having the formula (I):
##STR1##
in which R.sup.1 represents an alkyl group of 8 to 24 carbon atoms, an
alkoxyalkyl group of 8 to 24 carbon atoms, an alkyl group of 8 to 24
carbon atoms having a hydroxyl group, or an alkoxyalkyl group of 8 to 24
carbon atoms having a hydroxyl group, and each of R.sup.2 and R.sup.3
independently represents a hydrogen atom, an alkyl group of 1 to 12 carbon
atoms, an alkoxyalkyl of 1 to 12 carbon atoms, an alkyl group of 1 to 12
carbon atoms having a hydroxyl group, or an alkoxyalkyl group of 1 to 12
carbon atoms having a hydroxyl group, provided that R.sup.1 is not the
alkyl group in the case that R.sup.2 and R.sup.3 both represent a hydrogen
atom.
8) The image forming method wherein the amorphous organic polymer is
butyral resin or styrene/maleic acid half-ester resin.
9) The image forming method wherein the heat sensitive ink sheet has a
thickness of 0.2 to 0.6 .mu.m.
The following image receiving sheet is advantageously employed in the above
image forming method of the invention:
The image forming method which comprises a support sheet comprising a
porous sheet made of plastics and an image receiving layer provided
thereon, wherein the support sheet of the image receiving sheet is a
porous sheet which is sandwiched between a backing layer and an
anti-curling layer.
The following composite is advantageously employed in the above image
forming method of the invention:
The composite in which comprises an image receiving sheet having a support
sheet and an image receiving layer thereon and a heat sensitive ink sheet
having a base sheet and a heat sensitive ink layer thereon which are
superposed in such a manner that the heat sensitive ink layer is in
contact with the image receiving layer, said heat sensitive ink layer of
the heat sensitive ink sheet having a thickness of 0.2 to 0.1 .mu.m and
being formed of a heat sensitive ink material comprising 30 to 70 weight %
of colored pigment and 25 to 65 weight % of amorphous organic polymer
having a softening point of 40.degree. to 150.degree. C., and said support
sheet of the image receiving sheet comprising a porous sheet made of
plastics.
The preferred embodiments of the above-mentioned composite are the same as
described above 2) to 7).
There is also provided by the present invention an image forming method
which comprises the steps of:
superposing a heat sensitive ink sheet having a base sheet and a heat
sensitive ink layer thereon on an image receiving sheet having a support
sheet and an image receiving layer in such a manner that the heat
sensitive ink layer is in contact with the image receiving layer, said
heat sensitive ink layer of the heat sensitive ink sheet being formed of a
heat sensitive ink material which comprises colored pigment and
thermoplastic resin and said support sheet of the image receiving sheet
comprising a porous sheet made of plastics;
irradiating a laser beam modulated by digital signals on the heat sensitive
ink layer through the base sheet of the heat sensitive ink sheet to form
an image of the ink material on the image receiving layer; and
separating the base sheet of the heat sensitive ink sheet from the image
receiving sheet so that the image of the ink material can be retained on
the image receiving sheet (it is preferred that said image of the ink
material on the image receiving layer has an optical reflection density of
at least 0.5).
The preferred embodiments of the above-mentioned image forming method are
as follows:
1) The image forming method wherein the formation of the image of the ink
material on the image receiving sheet is done by ablation of the image
from the support of the heat sensitive ink sheet.
2) The image forming method further contains the steps of:
superposing the image receiving sheet on a white paper sheet in such a
manner that the image of the ink material is in contact with a surface of
the white paper sheet; and
separating the image receiving sheet from the white paper sheet, keeping
the image of the ink material on the white paper sheet (it is preferred
that said image of the ink material on the white paper sheet has an
optical reflection density of at least 1,0).
3) The image forming method wherein the support sheet of the image
receiving sheet is made of at least one material selected from the group
consisting of polyester, polyamide, polycarbonate, polyethersulfone,
polyimide, polyolefin, polyvinyl chloride, polyurethane, polyvinylidene
chloride, polyacrylate and cellulose acetate.
4) The image forming method the support sheet of the image receiving sheet
has a thickness of 50 to 300 .mu.m (preferably 75 to 200 .mu.m).
5) The image forming method wherein the support sheet of the image
receiving sheet is a porous sheet which is sandwiched between a backing
layer and an anti-curling layer, the image receiving layer being not
provided on the backing layer, and the image receiving layer being
provided on the curling layer.
6) The image forming method wherein the heat sensitive ink layer of the
heat sensitive ink sheet has a thickness of 0.2 to 1.0 .mu.m.
7) The image forming method wherein the image receiving layer of the image
receiving sheet comprises at least two layers (preferably comprises a
first image receiving layer and a second image receiving layer).
8) The image forming method wherein said heat sensitive ink layer of the
heat sensitive ink sheet is formed of a heat sensitive ink material
comprising 30 to 70 weight % of colored pigment and 30 to 70 weight % of
thermoplastic resin.
9) The image forming method wherein said thermoplastic resin is amorphous
organic polymer having a softening point of 40.degree. to 150.degree. C.
10) The image forming method wherein the heat sensitive ink sheet further
has a light-heat conversion layer between the base sheet and the heat
sensitive ink layer.
11) The image forming method wherein in the step of superposing a heat
sensitive ink sheet having a heat sensitive ink layer on an image
receiving sheet, the superposing is conducted in the application of
pressure of 1 to 30 kg/cm.sup.2 (preferably 2 to 10 kg/cm.sup.2)
12) The image forming method wherein the image receiving layer of the image
receiving sheet comprises a first receiving layer and a second receiving
layer thereon, the first receiving layer comprising at least one resin
selected from the group consisting of polyvinyl chloride, vinyl
chloride/vinyl acetate copolymer, vinyl chloride/vinyl alcohol copolymer
and vinyl chloride/vinyl acetate/maleic acid copolymer.
13) The image forming method wherein the image receiving layer of the image
receiving sheet comprises a first receiving layer and a second receiving
layer thereon, the second receiving layer comprising at least one resin
selected from the group consisting of polyvinyl butyral and alkyl
acrylate/acryl amide copolymer.
14) The image forming method wherein the image receiving layer of the image
receiving sheet comprises a first receiving layer and a second receiving
layer thereon, the first receiving layer having a thickness of 1 to 50
.mu.m (preferably 5 to 30 .mu.m) and the second receiving layer having a
thickness of 0.1 to 10 .mu.m (preferably 0.5 to 5 .mu.m).
The method of the invention can be utilized advantageously in preparation
of a color proof of full color type.
In more detail, the preparation of a color proof can be performed by the
steps of:
superposing a first heat sensitive ink sheet (such as a cyan ink sheet) on
an image receiving sheet;
placing imagewise a thermal head on the back (base sheet) of the first heat
sensitive ink sheet to form and transfer a color image (cyan image) of the
heat sensitive ink material onto the image receiving sheet;
separating the ink sheet from the image receiving sheet so that the color
image (cyan image) of the heat sensitive ink material is retained on the
image receiving sheet;
superposing a second heat sensitive ink sheet (such as a magenta ink sheet)
on the image receiving sheet having the cyan image thereon;
placing imagewise a thermal head on the back of the second heat sensitive
ink sheet to form and transfer a color image (magenta image) of the heat
sensitive ink material onto the image receiving sheet;
separating the ink sheet from the image receiving sheet so that the color
image (magenta image) of the heat sensitive ink material is retained on
the image receiving sheet;
superposing a third heat sensitive ink sheet (such as a yellow ink sheet)
on the image receiving sheet having the cyan image and magenta image
thereon;
placing imagewise a thermal head on the back of the second heat sensitive
ink sheet to form and transfer a color image (yellow image) of the heat
sensitive ink material onto the image receiving sheet;
separating the ink sheet from the image receiving sheet so that the color
image (yellow image) of the heat sensitive ink material is retained on the
image receiving sheet, whereby a multicolor image is formed on the image
receiving sheet; and
transferring thus prepared multicolor image onto a white paper sheet.
The image forming method of the invention employing the above heat
sensitive ink sheet and image receiving sheet, which uses a thermal head
or laser beam, is capable of giving an image which has dots having
preferable size and shape and good reproduction of gradation and which is
well analogous to a printed image. In more detail, the use of the plastic
sheet having fine pores as the support sheet of the image receiving sheet
gives cushion property or flexibility to the image receiving sheet, and
therefore pressure given by the thermal head in the transfer procedure or
by superposing brings about high and even adhesion between the ink layer
and the image receiving layer, which results in reduction of image
defects. Further, the use of the plastic sheet scarcely brings about
occurrence of trouble during running of the sheet in a thermal transfer
printer because the sheet is reduced in weight. Furthermore, the soft
sheet almost absorbs the deformation to be formed by incorporation of dust
between the sheets in the procedure to reduce defects of the resultant
image.
Moreover, in an image forming method using a laser beam, high sensibility
can be obtained because the image receiving sheet has low heat
conductivity due to fine pores.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a particle size distribution of cyan pigment employed in
Example 1.
FIG. 2 shows a particle size distribution of magenta pigment employed in
Example 1.
FIG. 3 shows a particle size distribution of yellow pigment employed in
Example 1.
In each figure, the axis of abscissas indicates particle size (.mu.m), the
left axis of ordinates indicates percentage (%) of particles of the
indicated particle sizes, and the right axis of ordinates indicates
accumulated percentage (%).
FIG. 4 shows a sectional view of a representative structure of the image
receiving sheet of the invention.
FIG. 5 shows a sectional view of a representative structure of the
composite of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The image forming method of the invention is utilized for thermal transfer
recording by area gradation using a thermal head or laser beam. The image
forming method of the invention is characterized in the use of a porous
sheet made of plastics which have fine pores therein as the support sheet
of the image receiving sheet. The heat sensitive ink layer of the heat
sensitive ink sheet is formed of a heat sensitive ink material which
comprises colored pigment and thermoplastic resin such as amorphous
organic polymer.
The image receiving sheet employed in the image forming method of the
invention comprises a support sheet (plastic support) and an image
receiving layer (heat adhesive layer) thereon.
The support sheet of the invention comprises a plastic sheet having fine
pores therein as mentioned above. Although the size of the pores is not
restricted, the pores are preferably present evenly throughout the whole
area of the support. Such a sheet can be, for example, prepared by a known
process comprising the steps of adding inorganic or organic particles to a
thermoplastic resin and stretching the resin to form apertures (pores)
around the particles; the steps of extruding an organic solvent solution
of a polymer from an orifice and dipping the polymer solution in a
solidifying medium to remove the solvent, whereby apertures (pores)
produced by removal of the solvent are formed; or the steps of extruding a
resin together with a blowing agent from an orifice, and forming pores.
Examples of plastic materials of the support sheet include polyesters such
as polyethylene terephthalate (PET) and polyethylene naphthalate;
polyamide; polycarbonate; polyethersulfone; polyimide; polyolefins such as
polyethylene and polypropylene; polyvinyl chloride; polyurethane;
polyvinylidene chloride; polyacrylates such as PMMA (polymethyl
methacrylate) and cellulose acetates such as cellulose triacetate.
Preferred are a polyethylene terephthalate and polypropylene. Especially,
polyethylene terephthalate is preferred from the viewpoint of dimensional
stability. In the case of the image forming method using a thermal head,
the thickness of the support generally is in the range of 50 to 250 .mu.m,
and preferably in the range of 75 to 150 .mu.m. In the case of the image
forming method using a laser beam, the thickness of the support generally
is in the range of 50 to 300 .mu.m, and preferably in the range of 75 to
200 .mu.m.
The support sheet preferably is a porous sheet which is sandwiched between
a backing layer and an anti-curling layer. The image receiving layer is
not provided on the backing layer, but provided on the anti-curling layer.
The structure of the image receiving sheet comprising the above support
sheet and the image receiving layer (mentioned later) is shown in FIG. 4.
In FIG. 4, the support sheet is composed of a porous plastic sheet 41 and
the backing layer 42 on the back and the anti-curling layer 43 on the
other side, and the image receiving layer 44 is provided on the
anti-curling layer 43. The backing layer functions as lubricating layer to
improve running property in a printer. The anti-curling layer is generally
provided to prevent curling of the sheet produced by the provision of the
backing layer.
The backing layer comprises a binder resin and fine particles, and further
may contain additives if desired. Examples of the resin include polyester
such as polyethylene terephthalate (PET) and polyethylene naphthalate;
polyamide; polycarbonate; polyethersulfone; polyimide; polyolefins such as
polyethylene and polypropylene; polyvinyl chloride; polyurethane;
pollvinylidene chloride; polyacrylates such as PMMA (polymethyl
methacrylate); and cellulose acetates such as cellulose triacetate.
Polyesters are preferred from the viewpoint of adhesion.
Examples of the particles include inorganic particles such as barium
sulfate, aluminium hydroxide, titanium dioxide, synthetic silica
(amorphous), magnesium carbonate, calcium carbonate, calcium silicate,
aluminium silicate and magnesium silicate; and organic particles such as
particles of carbon fluoride and polytetrafluoroethylene. Preferred are
calcium carbonate and titanium dioxide from the viewpoint of cost. The
mean particle size preferably is in the range of 0.1 to 10 .mu.m,
especially 0.3 to 3 .mu.m from the viewpoint of dispersibility, matte
effect and lubricating property.
The anti-curling layer generally comprises materials similar to those of
the backing layer, preferably the same materials as those of the backing
layer.
These layers may contain an antistatic agent or a surface-active agent.
Further, on these layers, an antistatic layer may be provided.
The backing layer and anti-curling layer generally have a thickness of 0.5
to 30 .mu.m.
The support sheet having the backing layer and anti-curling layer can be
prepared, for example, by the known method comprising coating liquids for
forming the backing layer and the anti-curling layer on the support sheet
having fine pores; or laminating the films of the backing layer and the
anti-curling layer on the support sheet having fine pores. Further, the
support sheet can be prepared by extruding a resin for the support sheet
under heating and then monoaxially stretching the resin, subsequently
superposing the extruded resins for the backing layer and ant-curling
layer on the stretched resin, and then stretching the composite in a
direction perpendicular to the monoaxially stretched direction. This
extruded method is preferred from the viewpoint of productivity. The
support sheet having the backing layer and anti-curling layer prepared by
the extruded method, is available as a commercial polyester film (e.g.,
Lumirror E60, E60L and E68L available from Toray Industries, Inc.; W900E
available from Diawhiel Co., Ltd.; Crysper G1212 available from Toyobo
Co., Ltd.). Lumirror E60L and Lumirror E68L have the following physical
properties:
density=0.8-0.9 g/cm.sup.3, surface roughness(SRa)=approx.0.1 .mu.m, and
smoothing degree (Beck)=approx. 13,000 sec.
The backing layer and anti-curling layer may have pores therein. The pores
can be produced by dispersing the particles in the resin.
A surface of the support sheet (or the anti-curling layer) on which the
image receiving layer is formed may be subjected to a coating treatment,
or surface treatment such as corona discharge treatment or glow discharge
treatment to enhance adhesion. Further an undercoat layer may be formed on
the surface of the support. The undercoat layer is not restricted so long
as it increases adhesion between the support and the image receiving
layer. Preferred material for the undercoat layer is silane coupling
agent. Furthermore, the surface of the support may be subjected to
antistatic treatment or matting treatment.
The image receiving layer provided on the support sheet may comprise a
single layer or two or more layers. The image receiving layer generally
comprises a first image receiving layer provided on the support and a
second image receiving layer provided on the first image receiving layer.
The first image receiving layer generally has Young's modulus of not more
than 200 kg.multidot.f/cm.sup.2 at room temperature. Use of polymer having
low Young's modulus gives cushioning characteristics to the image
receiving layer, whereby transferring property is improved to give high
recording sensibility, good quality of dot and satisfactory
reproducibility of gradation. Further, even if dust or dirt is present
between the heat sensitive ink sheet and the image receiving sheet which
are superposed for recording, the recorded image (transferred image)
hardly has defect due to the cushioning characteristics of the first image
receiving sheet. Furthermore, when the image transferred onto the image
receiving sheet is retransferred onto a white paper sheet for printing by
applying pressure and heat, the retransferring is conducted while the
first image receiving layer cushions variation of pressure depending upon
unevenness of a surface of the paper sheet. Therefore, the image
retransferred shows high bonding strength to the white paper sheet, and
further an image (having the second receiving layer thereon) obtained by
transferring an image which is formed on the second receiving layer
(described later) provided on the first receiving layer together with the
second receiving layer onto a white paper, shows a surface of a high gloss
to give an image which is well analogous to a printed image.
Examples of polymer materials employed in the first image receiving layer
include polyolefins such as polyethylene and polypropylene; copolymers of
ethylene and other monomer such as vinyl acetate or acrylic acid ester;
polyvinyl chloride; copolymers of vinyl chloride and other monomer such as
vinyl acetate, vinyl alcohol or maleic acid; polyvinylidene chloride;
copolymer containing vinylidene chloride; polyacrylate; polymethacrylate;
polyamides such as copolymerized nylon and N-alkoxymethylated nylon;
synthetic rubber; acrylic rubber; and chlorinated rubber. Preferred are
polyvinyl chloride, copolymer of vinyl chloride and vinyl acetate,
copolymer of vinyl chloride and vinyl alcohol and copolymer of vinyl
chloride, vinyl acetate and maleic acid. The degree of polymerization
preferably is in the range of 200 to 2,000.
The preferred polymer and copolymer are suitable for material of the first
image receiving layer due to the following reason:
(1) The polymer and copolymer show no tackiness at room temperature. (2)
The polymer and copolymer have low Young's modulus (modulus of elasticity)
and therefore are capable of easily following up unevenesss of a transfer
image in the heat transfer procedure. (3) Young's modulus can be easily
controlled because the polymer and copolymer have a number of plasticizers
showing good compatibility. (4) Bonding strength to other layer or film
can be easily controlled because the polymer and copolymer have a polar
group such as hydroxyl or carboxyl.
Polymer materials employed in the first image receiving layer may further
contain a plasticizer to supplement cushion characteristics. Example of
the plasticizer include phthalic acid esters (e.g., dibutyl phthalate,
dioctyl phthalate and butyl benzyl phthalate); aliphatic dibasic acid
esters (e.g., di(2-ethylhexyl) adipate and di(2-ethylhexyl) sebacate);
phosphoric acid triesters (e.g., tricresyl phosphate); polyol acid esters
(e.g., polyethylene glycol acid ester); epoxy compounds (e.g., epoxy fatty
acid ester); and (meth)acrylic acid esters (e.g., polyethylene glycol
dimethacrylate and pentaerythritol triacrytate).
Further, the first receiving layer may contain other various polymer,
surface-active agent, surface lubricant or agent for improving adhesion,
in order to control bonding strength between the first receiving sheet and
the support or the second image receiving layer. Furthermore, the first
image receiving layer preferably contain a tacky polymer (tackifier) in a
small amount to reduce Young's modulus, so long as the layer has no
tackiness.
For example, addition of fluorine-containing surface-active agent give
improvement of dot shape by improving wetting property between the ink
layer and the image receiving layer as well as reduction of the bonding
strength between the layers. However, the excess addition reduces the
bonding strength between the ink layer and the image receiving layer to
give poor dot shape. Thus the surface-active agent or surface lubricant
(e.g., fluorine-containing surface-active agent as above) is preferably
added to the polymer material in an amount of 0.0001 to 5 weight %,
especially in an amount of 0.001 to 3 weight %.
In the case that polyvinyl chloride or copolymer containing vinyl chloride
unit is employed, an organic tin-type stabilizer such as or is preferably
incorporated into the polymer or copolymer.
A thickness of the first image receiving layer preferably is in the range
of 1 to 50 .mu.m, especially 5 to 30 .mu.m. The thickness is determined by
the following reasons: 1) the thickness should be larger than a depth of
evenness of surface of the white paper sheet, 2) the thickness should be
that capable of absorbing a thickness of the overlapped portion of a
number of color images, 3) the thickness should be that capable of
absorbing dust stuck onto the image receiving layer or the ink layer in
the procedure of superposing the heat sensitive ink sheet and image
receiving sheet, and 4) the thickness should have sufficient cushioning
characteristics.
The image of the heat sensitive material which has been transferred on the
second image receiving layer of the image receiving sheet having the first
and second image receiving layers, is further retransferred onto the white
paper sheet. In the procedure, the second image receiving layer is
transferred on the white paper sheet together with the image. Hence, a
surface of the image on the white paper sheet has a gloss analogous to
that of a printed image with subjecting to no surface treatment such as
matting treatment, due to the second image receiving layer provided on the
image. Further, the second image receiving layer improves scratch
resistance of the retransferred image.
The second image receiving layer preferably comprises a polymer although
the layer can be made of various materials. Examples of these polymers
include polyolefins such as polyethylene and polypropylene; copolymers of
ethylene and other monomer such as vinyl acetate or acrylic acid ester;
polyvinyl chloride; copolymers of vinyl chloride and other monomer such
vinyl acetate, vinyl alcohol or maleic acid; copolymer containing
vinylidene chloride; polystyrene; copolymer of styrene and other monomer
such as maleic acid ester; polyvinyl acetate; butyral resin; modified
polyvinyl alcohol; copolymer of alkyl acrylate and acrylamide; polyamides
such as copolymerized nylon and N-alkoxymethylated nylon; synthetic
rubber; chlorinated rubber; phenol resin; epoxy resin; urethane resin;
urea resin; melamine resin; alkyd resin; maleic acid resin; copolymer
containing hydroxystyrene; sulfonamide resin; rosin ester; celluloses; and
rosin. Preferred are butyral resin and copolymer of alkyl acrylate and
acrylamide.
The second image receiving layer can contain a surface-active agent,
surface lubricant, plasticizer or agent for improving adhesion in order to
control bonding strength between the second image receiving layer and the
first image receiving layer or the heat sensitive ink layer. Further, it
is preferred to employ a solvent not to dissolve or swell the resin
contained in the first image receiving layer as a solvent used in a
coating liquid for forming the second image receiving layer. For example,
when polyvinyl chloride, which easily dissolves in various solvents, is
used as a resin of the first image receiving layer, a solvent used in the
coating liquid of the second image receiving layer preferably is alcohols
or solvents mainly containing water.
A thickness of the second receiving layer preferably is in the range of 0.1
to 10 .mu.m, especially 0.5 to 5.0 .mu.m. The thickness exceeding 10 .mu.m
damages unevenness of the transferred image derived from an uneven surface
of the white paper sheet (onto which the image on the image receiving
sheet is retransferred) and therefore the transferred image is not near to
a printed image due to its high gloss.
In order to control the bonding strength between the first and second image
receiving layers, solvents contained in the coating solution of the first
and second image receiving layers are selected as mentioned above; further
for example, the materials of the first and second image receiving layers
are used in combination of hydrophilic polymer and liophilic polymer, in
combination of polar polymer and nonpolar polymer, or as the additives
such as surface-active agent, surface lubricant such as a
fluorine-containing compound or silicone-containing compound, plasticizer
or agent for improving adhesion such as silane coupling agent are
appropriately used.
On the second image receiving layer, a lubricating layer (overcoating
layer) can be provided to improve lubricating property and scratch
resistance of a surface of the second image receiving layer.
Examples of materials forming the layer include a higher fatty acid (e.g.,
palmitic acid or stearic acid), a metal salt of a fatty acid (e.g., zinc
stearate), a fatty acid derivative (e.g., fatty acid ester, its partial
saponification product or fatty acid amide), a higher alcohol, a polyol
derivative (e.g., ester of polyol), wax (e.g., paraffin wax, carnauba wax,
montan wax, bees wax, Japan wax, or candelilla wax), cationic surfactant
(e.g., ammonium salt having long aliphatic chain group or pyridinium
salt), anionic and nonionic surfactants having a long aliphatic chain
group, and perfluoro-type surfactant.
An intermediate layer can be provided between the first and second image
receiving layers, in order to control transferring property.
The above explanation of the image receiving sheet corresponds to the case
that cushion property is given to the first image receiving layer of the
image receiving sheet. Alternatively, both of cushion property and
function for forming an image can be given to the second image receiving
layer of the image receiving sheet. In this case, the first image
receiving sheet functions as a peeling layer. In also such image receiving
layers, the same materials as mentioned previously can be employed.
The above structure of the image receiving sheet is especially useful in
the image forming method using a laser beam.
The image receiving layer may consist of a single layer. As the single
layer, the above second image receiving layer can be employed. The single
layer preferably has a thickness of 0.2 to 50 .mu.m, especially 0.5 to 20
.mu.m.
The heat sensitive ink sheet has a base sheet and a heat sensitive ink
layer which is formed of a heat sensitive ink material comprising colored
pigment and thermoplastic resin. The sheet having such an ink layer can be
employed in the image forming method using a laser beam.
In the image forming method using a thermal head, the heat sensitive ink
sheet has a base sheet and a heat sensitive ink layer having a thickness
of 0.2 to 1.0 .mu.m which is formed of a heat sensitive ink material
comprising 30 to 70 weight % of colored pigment and 25 to 65 weight % of
amorphous organic polymer having a softening point of 40.degree. to
150.degree. C. The sheet also corresponds to the preferred embodiment in
the image forming method using a laser beam.
The heat sensitive ink sheet can be particularly utilized in the formation
of multigradation image (especially multicolor image) by area gradation
(multi-valued recording), while the sheet can be naturally utilized in
binary recording.
As the base sheet, any of the materials of the support sheet employed in
the conventional fused ink transfer system and sublimation ink transfer
system can be employed. Preferably employed is a polyester film of approx.
5 .mu.m thick which has been subjected to release treatment.
In the image forming method using a laser beam, the base sheet is generally
made of materials through which light passes. Examples of the materials
include polyethylene terephthalate (PET), polycarbonate, polyethylene,
polyvinyl chloride, pollvinylidene chloride, polystyrene and
styrene/acrylonitrile copolymer. Preferred are a polyethylene
terephthalate and polypropylene. Especially, biaxially oriented
polyethylene terephthalate is preferred from the viewpoint of mechanical
strength and dimensional stability. The surface of the base sheet may be
subjected to glow discharge or corona discharge treatment. The thickness
of the base sheet generally is in the range of 10 to 200 .mu.m, and
preferably in the range of 20 to 150 .mu.m. Further, a undercoat layer may
be formed on the surface of the base sheet, if desired. The undercoat
layer are preferably formed of materials showing good adhesion and
excellent heat resistance. Preferred is polystyrene having small heat
conductivity in order to depress reduction of the sensitivity caused by
heat conductive. The thickness of the undercoat layer is generally in the
range of 0.01 to 2 .mu.m.
The colored pigment to be incorporated into the heat sensitive ink layer of
the invention can be optionally selected from known pigments. Examples of
the known pigments include carbon black, azo-type pigment,
phthalocyanine-type pigment, qunacridone-type pigment, thioindigo-type
pigment, anthraquinone-type pigment, and isoindolin-type pigment. These
pigments can be employed in combination with each other. A known dye can
be employed in combination with the pigment for controlling hue of the
color image.
The heat transfer ink layer of the invention contains the pigment in an
amount of 30 to 70 weight % and preferably in an amount of 30 to 50 weight
%. When the amount of the pigment is not less than 30 weight %, it is
difficult to form an ink layer of the thickness of 0.2 to 1.0 .mu.m which
shows a high reflection density. Moreover, the pigment preferably has such
particle distribution that at least 70 weight % of the pigment particles
has a particle size of not less than 1.0 .mu.m. A pigment particle of
large particle size reduces transparency of the formed image, particularly
in the area in which a number of color images are overlapped. Further,
large particles bring about difficulty to prepare the desired ink layer
satisfying the relationship between the preferred thickness and reflection
density.
Any of amorphous organic polymers having a softening point of 40.degree. to
150.degree. C. can be employed for the preparation of the ink layer of the
heat sensitive ink sheet of the invention. A heat-sensitive ink layer
using an amorphous organic polymer having a softening point of lower than
40.degree. C. shows unfavorable adhesion, and a heat-sensitive ink layer
using an amorphous organic polymer having a softening point of higher than
150.degree. C. shows poor sensitivity. Examples of the amorphous organic
polymers include butyral resin, polyamide resin, polyethyleneimine resin,
sulfonamide resin, polyester-polyol resin, petroleum resin, homopolymers
and copolymers of styrene or its derivatives (e.g., styrene, vinyltoluene,
.alpha.-methylstyrene, 2-methylstyrene, chlorostyrene, vinylbenzoic acid,
sodium vinylbenzenesulfonate and aminostyrene), and homopolymers and
copolymers of methacrylic acid or its ester (e.g., methacrylic acid,
methyl methacrylate, ethyl methacrylate, butyl methacrylate, and
hydroxyethyl methacrylate), homopolymers and copolymers of acrylic acid or
its ester (e.g., acrylic acid, methyl acrylate, ethyl acrylate, butyl
acrylate, and .alpha.-ethylhydroxy acrylate), homopolymers and copolymers
of a diene compound (e.g., butadiene and isoprene), and homopolymers and
copolymers of other vinyl monomers (e.g., acrylonitrile, vinyl ether,
maleic acid, maleic acid ester, maleic anhydride, cinnamic acid, vinyl
chloride, and vinyl acetate). Further, there can be mentioned copolymers
of at least two monomers selected from acrylic acid, its ester,
methacrylic acid, its ester, a diene compound and other vinyl monomers,
which are described above. These resins and polymers can be employed in
combination.
Particularly preferred are butyral resin and styrene/maleic acid half ester
resin, from the viewpoint of good dispersibility of the pigment.
Examples of trade names of the butyral resin include Denka butyral #2000-L
(softening point: 57.degree. C. (measured by DSC (Differential Scanning
Calorimeter); degree of polymerization: approx. 300) and Denka butyral
#4000-1 (softening point: 57.degree. C.; degree of polymerization: approx.
920) which are available from Denki Kagaku Kogyo Co., Ltd.; and Eslec
BX-10 (softening point: 72.degree. C.; Tg: 74.degree. C.; degree of
polymerization: 80; acetyl value: 69 molar %) and Eslec BL-S (Tg:
61.degree. C., viscosity: 12 cps in 5 weight % ethanol/toluene ›1/1 by
weight! solution) which are available from Sekisui Chemical Co., Ltd.
In the heat sensitive ink sheet of the invention, the ink layer contains
the amorphous organic polymer having a softening point of 40.degree. to
150.degree. C. in an amount of 25 to 65 weight % (30 to 70 weight % in the
method using laser beam), and preferably in an amount of 30 to 50 weight
%.
In the invention, it is preferred that both of the heat sensitive ink layer
and the second image receiving layer contain the same polymer or the same
kind polymer each other.
The heat sensitive ink layer preferably contains a nitrogen-containing
compound. The nitrogen-containing compound preferably is an amide compound
having the formula (I) described above, an amine compound, a quaternary
ammonium salt having the formula (II) or formula (III) described above,
hydarazine, aromatic amine or a heterocyclic compound. Preferred is an
amide compound having the formula (I).
The amide compound having the formula (I) is explained.
##STR2##
in which R.sup.1 represents an alkyl group of 8 to 24 carbon atoms, an
alkoxyalkyl group of 8 to 24 carbon atoms, an alkyl group of 8 to 24
carbon atoms having a hydroxyl group, or an alkoxyalkyl group of 8 to 24
carbon atoms having a hydroxyl group, and each of R.sup.2 and R.sup.3
independently represents a hydrogen atom, an alkyl group of 1 to 12 carbon
atoms, an alkoxyalkyl of 1 to 12 carbon atoms, an alkyl group of 1 to 12
carbon atoms having a hydroxyl group, or an alkoxyalkyl group of 1 to 12
carbon atoms having a hydroxyl group, provided that R.sup.1 is not the
alkyl group in the case that R.sup.2 and R.sup.3 both represent a hydrogen
atom.
In the formula (I), R.sup.1 generally is an alkyl group of 8 to 18 carbon
atoms, an alkoxyalkyl group of 8 to 18 carbon atoms, an alkyl group of 8
to 18 carbon atoms having a hydroxyl group, or an alkoxyalkyl group of 8
to 18 carbon atoms having a hydroxyl group. R.sup.1 preferably is an alkyl
group of 8 to 18 carbon atoms (especially 12 to 18 carbon atoms) or an
alkyl group of 8 to 18 carbon atoms (especially 12 to 18 carbon atoms)
having a hydroxyl group.
R.sup.2 generally represents a hydrogen atom, an alkyl group of 1 to 10
carbon atoms (especially 1 to 8 carbon atoms), an alkoxyalkyl group of 1
to 10 carbon atoms (especially 1 to 8 carbon atoms), an alkyl group of 1
to 10 carbon atoms having a hydroxyl group (especially 1 to 8 carbon
atoms), or an alkoxyalkyl group of 1 to 10 carbon atoms having a hydroxyl
group (especially 1 to 8 carbon atoms). R.sup.2 preferably is an alkyl
group of 1 to 10 carbon atom (especially 1 to 8 carbon atoms) or an alkyl
group of 1 to 10 carbon atom (especially 1 to 8 carbon atoms) having a
hydroxyl group.
R.sup.3 preferably is a hydrogen atom, an alkyl group of 1 to 4 carbon atom
(especially 1 to 3 carbon atoms). Especially, R.sup.3 preferably is a
hydrogen atom. Examples of the alkyl groups include methyl, ethyl,
isopropyl, n-propyl, n-butyl, isobutyl and tert-butyl.
However, R.sup.1 is not the alkyl group (i.e., R.sup.1 is the alkoxyalkyl,
the alkyl group having a hydroxyl group or the alkoxyalkyl having a
hydroxyl group), in the case that R.sup.2 and R.sup.3 both represent a
hydrogen atom.
The amide of the formula (I) can be prepared by reacting an acyl halide
with amine (by adding acyl halide to an aqueous alkaline solution
containing the amine) to introduce the acyl group into the amine, which is
performed, for example, according to Schotten-Baumann method. In more
detail, acyl halide is dropwise added to a chilled alkaline solution
containing amine, and operations such as addition and mixing are conducted
so as to maintain the reaction temperature of not higher than 15.degree.
C. In the reaction, use of amine, alkali and acyl halide in a ratio of
1:1:1 gives an amide compound.
In the case that amine which is sparingly soluble in water is used, an
ether solution containing tertiary amine is employed instead of the
aqueous alkaline solution. In more detail, an acyl halide is dropwise
added to an ether solution containing amine and triethylamine. In the
reaction, use of amine, triethylamine and an acyl halide in the ratio of
1:1:1 gives an amide compound. The obtained amide compound can be purified
by recrystallization if desired, to give a pure amide compound.
The amide compound of the formula (I) can be, for example, prepared by
using an acyl halide and amine in the combinations set forth in Table 1.
TABLE 1
______________________________________
Acyl Halide Amine
______________________________________
CH.sub.3 (CH.sub.2).sub.5 CH(OH)(CH.sub.2).sub.10 COCl
H.sub.2 NC.sub.2 H.sub.4 OH
CH.sub.3 (CH.sub.2).sub.5 CH(OH)(CH.sub.2).sub.10 COCl
NH.sub.3
n-C.sub.9 H.sub.19 COCl
CH.sub.3 NH.sub.2
n-C.sub.15 H.sub.31 COCl
CH.sub.3 NH.sub.2
n-C.sub.17 H.sub.35 COCl
CH.sub.3 NH.sub.2
n-C.sub.17 H.sub.35 COCl
n-C.sub.4 H.sub.9 NH.sub.2
n-C.sub.17 H.sub.35 COCl
n-C.sub.6 H.sub.13 NH.sub.2
n-C.sub.17 H.sub.35 COCl
n-C.sub.8 H.sub.17 NH.sub.2
n-C.sub.17 H.sub.35 COCl
H.sub.2 NC.sub.2 H.sub.4 OC.sub.2 H.sub.4 OH
n-C.sub.17 H.sub.35 COCl
(CH.sub.3).sub.2 NH
n-C.sub.17 H.sub.35 COCl
(C.sub.2 H.sub.5).sub.2 NH
______________________________________
Examples of the obtained amide compounds are shown in Table 2. The
compounds are indicated by R.sup.1, R.sup.2 and R.sup.3 of the formula
(I).
TABLE 2
______________________________________
R.sup.1 R.sup.2 R.sup.3
______________________________________
CH.sub.3 (CH.sub.2).sub.5 CH(OH)(CH.sub.2).sub.10
C.sub.2 H.sub.4 OH
H
CH.sub.3 (CH.sub.2).sub.5 CH(OH)(CH.sub.2).sub.10
H H
n-C.sub.9 H.sub.19
CH.sub.3 H
n-C.sub.15 H.sub.31
CH.sub.3 H
n-C.sub.17 H.sub.35
CH.sub.3 H
n-C.sub.17 H.sub.35
C.sub.2 H.sub.5
H
n-C.sub.17 H.sub.35
n-C.sub.4 H.sub.9
H
n-C.sub.17 H.sub.35
n-C.sub.6 H.sub.13
H
n-C.sub.17 H.sub.35
n-C.sub.8 H.sub.17
H
n-C.sub.17 H.sub.35
C.sub.2 H.sub.4 OC.sub.2 H.sub.4 OH
H
n-C.sub.17 H.sub.35
CH.sub.3 CH.sub.3
n-C.sub.17 H.sub.35
C.sub.2 H.sub.5
C.sub.2 H.sub.5
______________________________________
Subsequently, the quaternary ammonium salt of the formula (II) described
above is explained below.
##STR3##
in which R.sup.4 represents an alkyl group of 1 to 18 carbon atom or an
aryl group of 6 to 18 carbon atoms, each of R.sup.5, R.sup.6 and R.sup.7
independently represents a hydrogen atom, a hydroxyl group, an alkyl group
of 1 to 18 carbon atom or an aryl group of 6 to 18 carbon atoms, and
X.sub.1 represents a monovalent anion.
In the formula (II), R.sup.4 preferably is an alkyl group of 1 to 12 carbon
atom (especially 1 to 8 carbon atom) or an aryl group of 6 to 12 carbon
atoms (e.g., phenyl or naphthyl). Examples of the alkyl groups include
methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, tert-butyl,
n-pentyl, n-hexyl and n-octyl. Each of R.sup.5, R.sup.6 and R.sup.7
preferably is an alkyl group of 1 to 12 carbon atom (especially, 1 to 8
carbon atom) or an aryl group of 6 to 12 carbon atoms (e.g., phenyl or
naphthyl). X.sub.1 preferably is a halide ion, especially Cl.sup.- or
Br.sup.-.
Examples of the quaternary ammonium salts of the formula (II) include
ammonium chloride, tetra-n-butylammonium bromide and
triethylmethylammonium chloride.
The quaternary ammonium salt of the formula (III) described above is
explained below.
##STR4##
in which each of R.sup.8, R.sup.9, R.sup.10, R.sup.11, R.sup.12 and
R.sup.13 independently represents a hydrogen atom, a hydroxyl group, an
alkyl group of 1 to 18 carbon atom or an aryl group of 6 to 18 carbon
atoms, R.sup.14 represents an alkylene group of 1 to 12 carbon atom, and
X.sub.2 represents a monovalent anion.
The quaternary ammonium salt of the formula (III) is a dimmer of the
quaternary ammonium salt as described above, and the example includes
hexamethonium bromide ›i.e., hexamethylenebis(tri-methylammonium
bromide)!.
Examples of the amines mentioned above include cyclohexylamine,
trioctylamine and ethylenediamine.
Examples of the hydrazines include dimethylhydradine.
Examples of the aromatic amines include p-toluidine, N,N-dimethylaniline
and N-ethylaniline.
Examples of the heterocyclic compounds include N-methylpyrrole,
N-ethylpyridinium bromide, imidazole, N-methylquinolinium bromide and
2-methylbenzothiazole.
The heat sensitive ink layer generally contains 0.1 to 20 weight % of the
nitrogen-containing compound, and especially 1 to 10 weight % of the
compound. The compound preferably exists in the heat sensitive ink sheet
in the amount of 0.001 to 2 g per 1 m.sup.2, especially in the amount of
0.01 to 0.5 g per 1 m.sup.2.
The ink layer can further contain 1 to 20 weight % of additives such as a
releasing agent and/or a softening agent based on the total amount of the
ink layer so as to facilitate release of the ink layer from the support
when the thermal printing (image forming) takes place and increase
heat-sensitivity of the ink layer. Examples of the additives include a
higher fatty acid (e.g., palmitic acid and stearic acid), a metal salt of
a fatty acid (e.g., zinc stearate), a fatty acid derivative (e.g., fatty
acid ester and its partial saponification product), a higher alcohol, a
polyol derivative (e.g., ester of polyol), wax (e.g., paraffin wax,
carnauba wax, montan wax, bees wax, Japan wax, and candelilla wax), low
molecular weight polyolefin (e.g., polyethylene, polypropylene, and
polybutyrene) having a viscosity mean molecular weight of approx. 1,000 to
10,000, low molecular weight copolymer of olefin (specifically
.alpha.-olefin) with an organic acid (e.g., maleic anhydride, acrylic
acid, and methacrylic acid) or vinyl acetate, low molecular weight
oxidized polyolefin, halogenated polyolefin, homopolymer of acrylate or
methacrylate (e.g., methacylate having a long alkyl chain such as lauryl
methacrylate and stearyl methacrylate, and acrylate having a perfluoro
group), copolymer of acrylate or methacrylate with vinyl monomer (e.g.,
styrene), low molecular weight silicone resin and silicone modified
organic material (e.g., polydimethylsiloxane and polydiphenylsiloxane),
cationic surfactant (e.g., ammonium salt having a long aliphatic chain
group and pyridinium salt), anionic and nonionic surfactants having a long
aliphatic chain group, and perfluoro-type surfactant.
The compounds are employed singly or in combination with two or more kinds.
The pigment can be appropriately dispersed in the amorphous organic polymer
by conventional methods known in the art of paint material such as that
using a suitable solvent and a ball mill. The nitrogen-containing compound
and the additives can be added into the obtained dispersion to prepare a
coating liquid. The coating liquid can be coated on the support according
to a conventional coating method known in the art of paint material to
form the heat-sensitive ink layer.
The thickness of the ink layer is in the range of 0.2 to 1.0 m, and
preferably in the range of 0.3 to 0.6 .mu.m (more preferably in the range
of 0.3 to 0.5 .mu.m). An excessively thick ink layer having a thickness of
more than 1.0 .mu.m gives an image of poor gradation on the shadow portion
and highlight portion in the reproduction of image by area gradation. A
very thin ink layer having a thickness o less than 0.2 .mu.m cannot form
an image of acceptable optical reflection density.
In the method using a laser beam, the thickness of the ink layer is in the
range of 0.2 to 1.5 .mu.m, and preferably in the range of 0.2 to 1.0 .mu.m
(more preferably in the range of 0.2 to 0.6 .mu.m ). An excessively thick
ink layer having a thickness of more than 1.5 .mu.m gives an image of poor
gradation on the shadow portion and highlight portion in the reproduction
of image by area gradation. A very thin ink layer having a thickness o
less than 0.2 .mu.m cannot form an image of acceptable optical reflection
density.
The heat-sensitive ink layer of the invention mainly comprises a pigment
and an amorphous organic polymer, and the amount of the pigment in the
layer is high, as compared with the amount of the pigment in the
conventional ink layer using a wax binder. Therefore, the ink layer of the
invention shows a viscosity of higher than 10.sup.4 cps at 150.degree. C.
(the highest thermal transfer temperature), while the conventional ink
layer shows a viscosity of 10.sup.2 to 10.sup.3 cps at the same
temperature. Accordingly, when the ink layer of the invention is heated,
the ink layer per se is easily peeled from the support and transferred
onto an image receiving layer keeping the predetermined reflection
density. Such peeling type transfer of the extremely thin ink layer
enables to give an image having a high resolution, a wide gradation from a
shadow potion to a highlight portion, and satisfactory edge sharpness.
Further, the complete transfer (100%) of image onto the image receiving
sheet gives desired uniform reflection density even in a small area such
as characters of 4 point and a large area such as a solid portion.
The composite of the invention comprises the image receiving sheet
comprising the support sheet and the image receiving layer and the heat
sensitive ink sheet, which are described above. The composite is
advantageously employed in the following image forming methods. The
structure of the composite is shown in FIG. 5.
In FIG. 5, the heat sensitive ink sheet 53 is superposed on the image
receiving layer 52 of the image receiving sheet comprising the support
sheet 51 and the image receiving layer 52 to constitute the composite.
Subsequently, the image forming method of the invention is described below.
The image forming method (thermal transfer recording) of the invention can
be, for example, performed by means of a thermal head (generally using as
thermal head printer) using the above heat sensitive ink sheet and the
above image receiving sheet.
The method utilizing the thermal head can be conducted by the steps of:
superposing the heat sensitive ink sheet having the heat sensitive ink
layer on the image receiving sheet (formation of composite of the
invention); placing imagewise a thermal head the back (the base sheet) of
the heat sensitive ink sheet to form and transfer an image of the heat
sensitive ink material of the ink layer onto the image receiving sheet
(generally the second image receiving layer) by separating the ink sheet
from the image receiving sheet. The formation of the image using the
thermal head is generally carried out utilizing area gradation. The
transferred image onto the image receiving layer has an optical reflection
density of at least 1.0.
For conducting the formation of the image, the heat sensitive ink sheet is
laminated on the image receiving sheet using a laminator in such a manner
that the heat sensitive ink layer is in contact with the image receiving
layer to prepare a composite, and this composite can be employed.
Subsequently, the following procedures can be performed. After a white
paper sheet is prepared, the image receiving sheet having the transferred
image is superposed on the white paper sheet, which generally is a support
for printing, in such a manner that the transferred image is in contact
with a surface of the white paper sheet, and the composite is subjected to
pressing and heating treatments, and the image receiving sheet (having the
first image receiving layer) is removed from the composite whereby the
retransferred image can be formed on the white paper sheet (together with
the second image receiving layer). The transferred image onto the white
paper sheet has an optical reflection density of at least 1.0.
The above formation of the image can be generally conducted using the
thermal head printer by means of area gradation.
Further, the method similar to the above-mentioned image forming method can
be conducted using a laser beam instead of the thermal head. The image
forming method (thermal transfer recording method) utilizing the a laser
beam can utilize methods (i.e., ablation method) described in U.S. Pat.
No. 5,352,562 and Japanese Patent Provisional Publication No.
6(1994)-219052. The method of Japanese Patent Provisional Publication No.
6(1994)-219052 is performed by the steps of: superposing a heat sensitive
ink sheet comprising a base sheet and a heat sensitive ink layer (image
forming layer) between which a light-heat conversion layer capable of
converting an absorbed laser beam into heat energy and a heat sensitive
peeling layer containing heat sensitive material capable of producing a
gas by absorbing the heat energy (or only a light-heat conversion layer
further containing the heat sensitive material) are provided on the image
receiving sheet in such a manner that the heat sensitive ink layer is in
contact with a surface of the image receiving sheet; irradiating imagewise
a laser beam on the composite (the heat sensitive ink sheet and the image
receiving sheet) to enhance temperature of the light-heat conversion
layer; causing ablation by decomposition or melting of materials of the
light-heat conversion layer and decomposing a portion of the heat
sensitive peeling layer to produce a gas, whereby bonding strength between
the heat sensitive ink layer and the light-heat conversion layer reduces;
and transferring the heat sensitive ink layer corresponding to the portion
onto the image receiving layer.
The above image forming method is usually conducted using a laser recording
machine. First, the side (support sheet) having no image receiving layer
of the image receiving sheet is closely placed and fixed on a laser
recording drum by the means of suction, etc. (e.g., fixed on the drum by
sucking inside of the drum). Then, the ink layer of the heat-sensitive ink
sheet is placed on the image receiving layer of the image receiving sheet,
passed through a couple of rollers under pressure (if desired under
heating), whereby the heat-sensitive ink sheet and the image receiving
sheet are united to prepare a composite. The composite can be beforehand
prepared with using no laser recording drum by superposing the
heat-sensitive ink sheet on the image receiving sheet in such a manner
that the ink layer is in contact with the image receiving layer and
passing them under pressure (if desired under heating) through a couple of
rollers, and the composite can be also employed in the later procedure.
The pressure for preparing the composite is generally in the range of 1 to
30 kg/cm.sup.2, preferably in the range of 2 to 10 kg/cm.sup.2. The
procedure of passing the sheets under pressure through a couple of rollers
is preferably conducted under heating. The heating is conducted in such a
manner that the surfaces of the rollers are preferably heated at a
temperature of not higher than 250.degree. C., especially at a temperature
of 60.degree. to 150.degree. C. The support sheet of the image receiving
sheet is made of plastic sheet having fine pores therein, and therefore
the pressing procedure can be conducted under even pressure due to cushion
property and flexibility of the support sheet to form a composite in which
the heat sensitive ink sheet is closely superposed on the image receiving
sheet. When dust is stuck onto the image receiving layer or the ink layer
in the procedure of superposing the heat sensitive ink sheet and image
receiving sheet, the support sheet almost cushions deformation by dust to
reduce image defect.
Subsequently, a laser beam modulated by color separated image signals scans
the heat sensitive ink sheet of the composite on the recording drum with
rotating the drum, to record the signals. Then, the heat sensitive ink
sheet is peeled from the image receiving sheet to form a transferred image
on the image receiving sheet. The resultant image generally has area
gradation of an optical reflection density of at least 0.5.
Otherwise, in the above method using a laser beam, formation of the image
can be also conducted by the steps of portionwise melting the heat
sensitive ink layer by means of heat energy given by absorption of a laser
beam, and transferring the portion onto the image receiving sheet under
melting.
Further, the resultant transferred image formed on the image receiving
sheet is superposed on a white paper sheet (printing paper) which is
separately prepared, and the composite is pressed under heating to form a
retransferred image on the white paper sheet. The resultant image
generally has area gradation of an optical reflection density of at least
1.0.
In the above method using a laser beam (utilizing the ablation), a
light-heat conversion layer is preferably provided between tha base sheet
and the heat sensitive ink layer. Further, a heat sensitive peeling layer
is provided on the light-heat conversion layer in order to advantageously
conduct the ablation method. When the light-heat conversion layer combines
light-heat conversion function with heat sensitive peeling function, the
heat sensitive peeling layer may be not necessarily provided.
The light-heat conversion layer and heat sensitive peeling layer mentioned
above are explained below.
The light-heat conversion layer basically comprises a coloring material
(e.g., dye or pigment) and a binder.
Examples of the coloring material include black pigments such as carbon
black, pigments of large cyclic compounds such as phthalocyanine and
naphthalocyanine absorbing a light having wavelength from visual region to
infrared region, organic dyes such as cyanine dyes (e.g., indolenine
compound), anthraquinone dyes, azulene dyes and phthalocyanine dyes which
are employed as laser absorbing materials of high-density laser recording
media such as an optical disc, and dyes of organic metal compounds such as
dithiol nickel complex. The light-heat conversion layer preferably is as
thin as possible to enhance recording sensitivity, and therefore dyes such
as cyanine, phthalocyanine and naphthalocyanine having a large absorption
coefficient are preferably employed.
Examples of the binder include homopolymer or copolymer of acrylic monomers
such as acrylic acid, methacrylic acid, acrylic acid ester and methacrylic
acid ester; celluloses such as methyl cellulose, ethyl cellulose and
cellulose acetate; vinyl polymers such as polystyrene, vinyl
chloride/vinyl acetate copolymer, polyvinyl pyrrolidone, polyvinyl butyral
and polyvinyl alcohol; copolymer of vinyl monomers; polycondensation
polymers such as polyester and polyamide; and thermoplastic polymers
containing rubber (e.g., butadiene/styrene copolymer). Otherwise, the
binder may be a resin formed by polymerization or cross-linkage of
monomers such as epoxy compounds by means of light or heating.
A ratio between the amount of the coloring material and that of the binder
preferably is in the range of 1:5 to 10:1 (coloring material:binder),
especially in the range of 1:3 to 3:1. When the amount of the binder is
less than the lower limit, cohesive force of the light-heat conversion
layer lowers and therefore the layer is apt to transfer onto the image
receiving sheet together with the heat sensitive ink layer in the
transferring procedure. Further, the light-heat conversion layer
containing excess binder needs a large thickness to show a desired light
absorption, which occasionally results in reduction of sensitivity.
The thickness of the light-heat conversion layer generally is in the range
of 0.05 to 2 .mu.m, and preferably 0.1 to 1 .mu.m. The light-heat
conversion layer preferably shows light absorption of not less than 70% in
a wavelength of a used laser beam.
The heat sensitive peeling layer is a layer containing a heat sensitive
material. Examples of the material include a compound (e.g., polymer or
low-molecular weight compound) which is itself decomposed or changed by
means of heating to produce a gas; and a compound (e.g., polymer or
low-molecular weight compound) in which a relatively volatile liquid such
as water has been adsorbed or absorbed in marked amount. These compounds
can be employed singly or in combination of two kinds.
Examples of the polymers which are itself decomposed or changed by means of
heating to produce a gas include self-oxidizing polymers such as
nitrocellulose; polymers containing halogen atom such as chlorinated
polyolefin, chlorinated rubber, polyvinyl chloride and polyvinylidene
chloride; acrylic polymers such as polyisobutyl methacylate in which
relatively volatile liquid such as water has been adsorbed; cellulose
esters such as ethyl cellulose in which relatively volatile liquid such as
water has been adsorbed; and natural polymers such as gelatin in which
relatively volatile liquid such as water has been adsorbed.
Examples of the low-molecular weight compounds which are itself decomposed
or changed by means of heating to produce a gas include diazo compounds
and azide compounds.
These compounds which are itself decomposed or changed preferably produce a
gas at a temperature not higher than 280.degree. C., especially produce a
gas at a temperature not higher than 230.degree. C. (preferably a
temperature not lower than 100.degree. C.).
In the case that the low-molecular weight compound is employed as the heat
sensitive material of the heat sensitive peeling layer, the compound is
preferably employed together with the binder. The binder may be the
polymer which itself decomposes or is changed to produce a gas or a
conventional polymer having no property mentioned above. A ratio between
the low-molecular weight compound and the binder preferably is in the
range of 0.02:1 to 3:1 by weight, especially 0.05:1 to 2:1.
The heat sensitive peeling layer is preferably formed on the whole surface
of the light-heat conversion layer. The thickness preferably is in the
range of 0.03 to 1 .mu.m, especially 0.05 to 0.5 .mu.m.
The present invention is further described by the following Examples and
Comparison Examples. The term "part(s)" indicated in Example means "weight
part(s)".
EXAMPLE 1
(1) Preparation of heat sensitive ink sheet
The following three pigment dispersions were prepared:
______________________________________
A) Cyan pigment dispersion
Cyan Pigment (CI, P.B. 15:4)
12.0 parts
Binder solution 122.8 parts
B) Magenta pigment dispersion
Magenta Pigment (CI, P.R. 57:1)
12.0 parts
Binder solution 122.8 parts
C) Yellow pigment dispersion
Yellow Pigment (CI, P.Y. 14)
12.0 parts
Binder solution 122.8 parts
______________________________________
The binder solution comprised the following components:
______________________________________
Butyral resin (softening point: 57.degree. C.,
12.0 parts
Denka Butyral #2000-L, available from
Denki Kagaku Kogyo K.K.)
Solvent (n-propyl alcohol)
110.0 parts
Dispersing agent (Solsparese S-20000,
0.8 parts
available from ICI Japan Co., Ltd.)
______________________________________
The particle size distribution of the pigments in the dispersions are shown
in the attached figures, wherein FIG. 1 indicates the distribution of cyan
pigment; FIG. 2 indicates the distribution of magenta pigment; and FIG. 3
indicates the distribution of yellow pigment. In each figure, the axis of
abscissas indicates particle size (.mu.m), the left axis of ordinates
indicates percentage (%) of particles of the indicated particle sizes, and
the right axis of ordinates indicates accumulated percentage (%).
in FIG. 1, a median size of the particles is 0.154 .mu.m, the specific
surface is 422,354 cm.sup.2 /cm.sup.3, and 90% of the total particles have
particle sizes of not less than 0.252 .mu.m. in FIG. 2, a median size of
the particles is 0.365 .mu.m, the specific surface is 189,370 cm.sup.2
/cm.sup.3, and 90% of the total particles have particle sizes of not less
than 0.599 .mu.m. In FIG. 3, a median size of the particles is 0.364
.mu.m, the specific surface is 193,350 cm.sup.2 /cm.sup.3, and 90% of the
total particles have particle sizes of not less than 0.655 .mu.m.
To 10 parts of each pigment dispersion were added 0.24 part of
N-hydroxyethyl-12-hydoxystearic amide, 0.01 part of a surface active agent
(Megafack F-177, available from Dainippon Ink & Chemicals Inc.) and 60
parts of n-propyl alcohol to give a coating liquid. Each of thus obtained
coating liquids ›A), B) and C) corresponding to the pigment dispersions
A), B) and C)! was coated using a whirler on a polyester film (base sheet;
thickness: 5 .mu.m, available from Teijin Co., Ltd.) with a back surface
having been made easily releasable. Thus, a cyan ink sheet having a
support and a cyan ink layer of 0.36 .mu.m, a magenta ink sheet having a
support and a magenta ink layer of 0.38 .mu.m, and a yellow ink sheet
having a support and a yellow ink layer of 0.42 .mu.m, were prepared.
(2) Preparation of image receiving sheet
The following coating liquids for first and second image receiving layers
were prepared:
______________________________________
(Coating liquid for first image receiving layer)
Vinyl chloride/vinyl acetate copolymer
25 parts
(MPR-TSL, available from
Nisshin Kagaku Co., Ltd.)
Dibutyloctyl phthalate 12 parts
(DOP, Daihachi Kagaku Co., Ltd.)
Surface active agent 4 parts
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
Solvent 75 parts
(Methyl ethyl ketone)
(Coating liquid for second image receiving layer)
Butyral resin (Denka Butyral #2000-L, available
16 parts
from Denki Kagaku Kogyo K.K.)
N,N-dimethylacrylamide/butyl acrylate
4 parts
copolymer
Surface active agent 0.5 parts
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
Solvent 200 parts
(n-propyl alcohol)
______________________________________
The above coating liquid for first image receiving layer was coated on a
polyester film (support sheet) having fine pores therein (thickness: 100
.mu.m; trade name: Rumiler E60, available from Toray Industries, Inc.)
using a whirler, and dried for 2 minutes in an oven of 100.degree. C. to
form a first image receiving layer (thickness: 20 .mu.m) on the film.
Subsequently, the above coating liquid for second image receiving layer was
coated on the first image receiving layer using a whirler, and dried for 2
minutes in an oven of 100.degree. C. to form a second image receiving
layer (thickness: 2 .mu.m).
›Image formation using thermal head and its evaluation!
Using the heat sensitive ink sheets and the image receiving sheet obtained
in Examples 1, the image formation was performed as follows:
(1) Formation of transferred image (Step 1)
Initially, the cyan heat sensitive ink sheet was superposed on the image
receiving sheet, and a thermal head was placed on the cyan ink sheet side
for imagewise forming a cyan image by the known divided sub-scanning
method. The divided sub-scanning method was performed with multiple
modulation for giving area gradation by moving a thermal head of 75
.mu.m.times.50 .mu.m in one direction at a pitch of 3 .mu.m along 50 .mu.m
length. The base sheet (polyester film) of the cyan ink sheet was then
peeled off from the image receiving sheet on which a cyan image with area
gradation was maintained. On the image receiving sheet having the cyan
image was superposed the magenta ink sheet, and the same procedure was
repeated for forming a magenta image with area gradation on the image
receiving sheet having the cyan image. The yellow ink sheet was then
superposed on the image receiving sheet having the cyan and magenta images
thereon in the same manner, and the same procedure was repeated for
forming a yellow image with area gradation on the image receiving sheet.
Thus, a multicolor image was formed on the image receiving layer.
(2) Formation of retransferred image (Step 2)
Subsequently, an art paper sheet was placed on the image receiving sheet
having the multicolor image, and they were passed through a couple of heat
rollers under conditions of 130.degree. C., 4.5 kg/cm.sup.2 and 4 m/sec.
Then, the polyester film (support sheet) of the image receiving sheet was
peeled off from the art paper sheet to form a multicolor image having the
second image receiving layer on the art paper sheet. Thus obtained
multicolor image showed high approximation to that of chemical proof
(Color Art, available from Fuji Photo Film Co., Ltd.) prepared from a lith
manuscript.
The following is optical reflection density of a solid portion of each
color image:
Cyan image: 1.53
Magenta image: 1.43
Yellow image 1.58
(3) Evaluation of color image obtained in Step 1
The color image obtained in Step 1 was evaluated on occurrence of line on
image, nonuniformity of concentration, resistance to adhesion, running
property for auto paper feeding and shape of dot.
i) Shape of dot was ranked based on evaluation of multicolor image (AA)
obtained in Example 1, as follows:
(Shape of dot)
BB: a little unsatisfactory compared with dot forming multicolor image of
Example 1
CC: unsatisfactory compared with dot forming multicolor image of Example 1
ii) Occurrence of line and nonuniformity of concentration were evaluated by
visual observation of ten persons. They were ranked based on evaluation of
multicolor image (CC) obtained in Comparison Example 1 (mentioned later),
as follows:
AA: Excellent compared with gradation reproduction of multicolor image of
Comparison Example 1
BB: Good compared with gradation reproduction of multicolor image of
Comparison Example 1
iii) Ten sheets of image receiving sheets were set in a cassette for
feeding paper of a printer, and auto paper feeding was performed. The
feeding property was observed to be evaluated. It was ranked based on
evaluation of feeding property (CC) of the sheet obtained in Comparison
Example 1, as follows:
AA: Excellent compared with feeding property of the sheet of Comparison
Example 1
BB: Good compared with feeding property of the sheet of Comparison Example
1
iv) Resistance to adhesion was evaluated as follows: Five sheets of image
receiving sheets (samples) having a size of 5 cm.times.5 cm were allowed
to stand for one hour in an atmosphere of 23.degree. C., 60% RH. The
resultant samples were superposed in the same directions and a pair of
glass plates were arranged on both sides of the superposed samples to be
fixed. The composite was protected from moisture with wrapping. The
composite was allowed to stand for two hours under load of 2 kg. It was
observed whether the resultant samples (sheets) was stuck each other or
not. The result was ranked based on evaluation of resistance to adhesion
(CC) of the sheet obtained in Comparison Example 1, as follows:
AA: Excellent compared with the sheet of Comparison Example 1
BB: Good compared with the sheet of Comparison Example 1
Good resistance to adhesion means that the sheets are not stuck each other.
The results of these evaluation are set forth in Table 4.
EXAMPLES 2-4
The procedures of Example 1 were repeated except for employing as the
plastic support of the image receiving sheet plastic supports shown in
Table 3 to prepare three kinds of image receiving sheets, and heat
sensitive ink sheets (cyan ink sheet, magenta ink sheet and yellow ink
sheet).
A multicolor image was prepared in the same manner as Example 1 using the
heat sensitive ink sheets and one of the image receiving sheets prepared
in the same manner as Example 1. The resultant multicolor image was
retransferred onto an art paper sheet in the same manner as Example 1.
Optical reflection density of a solid portion of each color image was the
same as Example 1. The other evaluations in Step 1 were the same as
Example 1, and the results are set forth in Table 4.
Comparison Examples 1-2
The procedures of Example 1 were repeated except for employing as the
plastic support of the image receiving sheet plastic supports shown in
Table 3 to prepare three kinds of image receiving sheets, and heat
sensitive ink sheets (cyan ink sheet, magenta ink sheet and yellow ink
sheet).
A multicolor image was prepared in the same manner as Example 1 using the
heat sensitive ink sheets and one of the image receiving sheets prepared
in the same manner as Example 1. The resultant multicolor image was
retransferred onto an art paper sheet in the same manner as Example 1.
Optical reflection density of a solid portion of each color image was the
same as Example 1. The other evaluations in Step 1 were the same as
Example 1, and the results are set forth in Table 4.
TABLE 3
______________________________________
Thickness
Support sheet (.mu.m)
______________________________________
Ex. 1 Polyester film having fine pores
100
(trade name: Lumirror E60, available from
Toray Industries, Inc.)
Ex. 2 Polyester film having fine pores
100
(trade name: Limirror E68L, available from
Toray Industries, Inc.)
Ex. 3 Polyester film having fine pores
100
(trade name: W900E, available from
Diawhiel Co., Ltd.)
Ex. 4 Polyester film having fine pores
125
(trade name: Crysper G1212, available from
Toyobo Co., Ltd.)
Co. Ex. 1
Clear polyethylene terephthalate film
100
(trade name: Lumirror #100, available from
Toray Industries, Inc.)
Co. Ex. 2
White polyethylene terephthalate film
125
having no fine pore
(trade name: Lumirror X-20, available from
Toray Industries, Inc.)
______________________________________
TABLE 4
______________________________________
Occur- Nonuni- Resis- Running
Shape of rence formity tance to
prop-
Dot of line of conc. adhesion
erty
______________________________________
Ex. 1 AA AA AA AA AA
Ex. 2 AA AA AA AA AA
Ex. 3 AA AA AA AA AA
Ex. 4 AA AA AA AA AA
Co. Ex. 1
AA CC CC CC CC
Co. Ex. 2
AA CC CC BB BB
______________________________________
As is apparent from the results of Table 4, the image forming methods using
the image receiving sheet having fine pores therein (Examples 1-4) gave
transferred images having high quality. Further in the retransferred
images obtained from the transferred images, their surfaces were matted by
following up unevenness of a paper sheet and therefore the glosses were
those which are well analogous to a printed image.
Moreover, a composite of an image receiving sheet and a heat sensitive ink
sheet was previously prepared, and then the above image forming method was
conducted using the composite. Also in this case, the results of the above
evaluations were the same as in Examples 1-4.
EXAMPLE 5
The procedures of Example 1 were repeated except for changing the thickness
of the second image receiving layer form 2 .mu.m to 5 .mu.m and forming no
first image receiving layer, to prepare an image receiving sheet, and heat
sensitive ink sheets (cyan ink sheet, magenta ink sheet and yellow ink
sheet).
A multicolor image was prepared in the same manner as Example 1 using the
heat sensitive ink sheets and the image receiving sheet prepared in the
same manner as Example 1. The resultant multicolor image was retransferred
onto an art paper sheet in the same manner as Example 1.
Optical reflection density of a solid portion of each color image was the
same as Example 1. The other evaluations in Step 1 were the same as
Example 1 except for the following and the results are set forth in Table
6.
Basis of evaluation ranked as "CC" was changed from that obtained in
Comparison Example 1 to that obtained in Comparison Example 3 (mentioned
later).
Comparison Examples 3-4
The procedures of Example 5 were repeated except for employing as the
plastic support of the image receiving sheet plastic supports shown in
Table 5 to prepare three kinds of image receiving sheets, and heat
sensitive ink sheets (cyan ink sheet, magenta ink sheet and yellow ink
sheet).
A multicolor image was prepared in the same manner as Example 1 using the
heat sensitive ink sheets and the image receiving sheet prepared in the
same manner as Example 1. The resultant multicolor image was retransferred
onto an art paper sheet in the same manner as Example 1.
Optical reflection density of a solid portion of each color image was the
same as Example 1. The other evaluations in Step 1 were the same as
Example 5, and the results are set forth in Table 6.
TABLE 5
______________________________________
Thickness
Support sheet (.mu.m)
______________________________________
Ex. 1 Polyester film having fine pores
100
(trade name: Lumirror E60, available from
Toray Industries, Inc.)
Co. Ex. 3
Clear polyethylene terephthalate film
100
(trade name: Lumirror #100, available from
Toray Industries, Inc.)
Co. Ex. 4
White polyethylene terephthalate film
125
having no fine pore
(trade name: Lumirror X-20, available from
Toray Industries, Inc.)
______________________________________
TABLE 6
______________________________________
Occur- Nonuni- Resis- Running
Shape of rence formity tance to
prop-
Dot of line of conc. adhesion
erty
______________________________________
Ex. 1 BB BB BB BB BB
Co. Ex. 1
CC CC CC CC CC
Co. Ex. 2
CC CC CC BB BB
______________________________________
As is apparent from the results of Table 6, in the image forming method
using the image receiving sheet having fine pores therein, even use of
single image receiving layer gave transferred images having relatively
high quality.
EXAMPLE 6
Heat sensitive ink sheets and an image receiving sheet were prepared below.
Then, a composite of a heat sensitive sheet and an image receiving sheet
was irradiated with a laser beam to form a transferred image in the
following manner.
(1) Preparation of image receiving sheet
The coating liquid for first image receiving layer were preparedly mixing
the following components by the use of a stirrer:
______________________________________
(Coating liquid for first image receiving layer)
______________________________________
Vinyl chloride copolymer
9 parts
(Zeon 25, available from
Nippon Geon Co., Ltd.)
Surface active agent 0.1 part.sup.
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
Methyl ethyl ketone 130 parts
Toluene 35 parts
Cyclohexanone 20 parts
Dimethylformamide 20 parts
______________________________________
The above coating liquid for first image receiving layer was coated on a
polyester film (support sheet) having fine pores therein (thickness: 100
.mu.m; trade name: Lumirror E60L, available from Toray Industries, Inc.)
using a whirler, and dried for 2 minutes in an oven of 100.degree. C. to
form a first image receiving layer (thickness: 1 .mu.m) on the film.
The coating liquid for second image receiving layer were prepared by mixing
the following components by the use of a stirrer:
______________________________________
(Coating liquid for second image receiving layer)
______________________________________
Methyl methacrylate/ethyl acrylate/
17 parts
methacrylic acid copolymer
(Diyanal BR-77, available from
Mitsubishi Rayon Co., Ltd.)
Alkyl acrylate/alkyl methacrylate copolymer
17 parts
(Diyanal BR-64, available from
Mitsubishi Rayon Co., Ltd.)
Pentaerythritol tetraacrylate
22 parts
(A-TMMTN, available from
Shi Nakamura Kagaku Co., Ltd.)
Surface active agent 0.4 part.sup.
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
Methyl ethyl ketone 100 parts
Hydroquinone monomethyl ether
0.05 part.sup.
Photopolymerization initiator
1.5 parts
(2,2-dimethoxy-2-phenylacetophenone)
______________________________________
Subsequently, the above coating liquid for second image receiving layer was
coated on the first image receiving layer using a whirler, and dried for 2
minutes in an oven of 100.degree. C. to form a second image receiving
layer (thickness: 25 .mu.m).
(2) Preparation of heat sensitive ink sheet
1) Preparation of coating liquid for light-heat conversion layer
The following components were mixed using a stirrer to prepare a coating
liquid for light-heat conversion layer:
______________________________________
Dye absorbing infrared ray
1.7 part.sup.
(IR-820, available from
Nippo Kayaku Co., Ltd.)
Varnish of polyamic acid
13 parts
(PAA-A, available from
Mitsui Toatsu Chemicals, Inc.)
1-Methoxy-2-propanol 60 parts
Methyl ethyl ketone 88 parts
Surface active agent 0.05 part.sup.
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
______________________________________
2) Formation of light-heat conversion layer
A first subbing layer comprising styrene/butadiene copolymer (thickness:
0.5 .mu.m ) and a second subbing layer comprising gelatin (thickness: 0.1
.mu.m) were formed on a polyethylene terephthalate film (base sheet;
thickness: 75 .mu.m) in order. Then, the above coating liquid for
light-heat conversion layer was coated on the second subbing layer using a
whirler, and dried for 2 minutes in an oven of 100.degree. C. to form a
light-heat conversion layer (thickness: 0.2 .mu.m (measured by feeler-type
thickness meter, absorbance of light of 830 nm: 1.4)).
3) Preparation of coating liquid for heat sensitive peeling layer
The following components were mixed using a stirrer to prepare a coating
liquid for heat sensitive peeling layer:
______________________________________
Nitrocellulose 1.3 part.sup.
(HIG120, available from
Asahi Chemical Co., Ltd.)
Methyl ethyl ketone 26 parts
Propylene glycol monomethylether acetate
40 parts
Toluene 92 parts
Surface active agent 0.01 part.sup.
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
______________________________________
4) Formation of heat sensitive peeling layer
The above coating liquid for heat sensitive peeling layer was coated on the
light-heat conversion layer using a whirler, and dried for 2 minutes in an
oven of 100.degree. C. to form a heat sensitive peeling layer (thickness:
0.1 .mu.m (measured by feeler-type thickness meter a layer formed by
coating the liquid on a surface of a hard sheet in the same manner as
above)).
5) Preparation of coating liquid for heat sensitive ink layer (image
forming layer) of magenta
The following components were mixed using a stirrer to prepare a coating
liquid for heat sensitive ink layer for magenta image:
Preparation of mother liquor
______________________________________
Polyvinyl butyral 12.6 parts
(Denka Butyral #2000-L available
from Denki Kagaku Kogyo K.K.)
Magenta pigments 18 parts
(C.I. P.R. 57:1)
Dispersing agent 0.8 part.sup.
(Solspers S-20000,
available from ICI Japan Co., Ltd.)
n-Propyl alcohol 110 parts
Glass beads 100 parts
______________________________________
The above materials were placed in a paint shaker (available from Toyo
Seiki Co., Ltd.) and were subjected to dispersing treatment for two hours
to prepare the mother liquor. The obtained mother liquor was diluted with
n-propyl alcohol, and particle size distribution of the pigments in the
diluted liquid was measured by a particle size measuring apparatus
(utilizing laser beam scattering system). The measurement showed that the
pigments of not less than 70 weight % had particle size of 180 to 300 nm.
Preparation of coating liquid
______________________________________
Mother liquor prepared above
6 parts
n-Propyl alcohol 60 parts
Surface active agent 0.01 part.sup.
(Megafack F-177, available from
Dainippon Ink & Chemicals Inc.)
______________________________________
The above components were mixed with a stirrer to prepare a coating liquid
for forming a heat sensitive ink layer of magenta.
6) Formation of heat sensitive ink layer of magenta
The above coating liquid for heat sensitive ink layer of magenta image was
coated on the heat sensitive peeling layer using a whirler, and dried for
2 minutes in an oven of 100.degree. C. to form a heat sensitive ink layer
(thickness: 0.3 .mu.m (measured by feeler-type thickness meter a layer
formed by coating the liquid on a surface of a hard sheet in the same
manner as above)). The obtained ink layer showed optical transmission
density of 0.7 (measured by Macbeth densitometer using green filter).
Thus, a heat sensitive ink sheet (magenta image) composed of a base sheet,
a light-heat conversion layer, a heat sensitive peeling layer and heat
sensitive ink layer of magenta image, was prepared.
›Formation of image by laser beam and evaluation!
(3) Preparation of Composite for Forming Image
The above heat sensitive ink sheet and the above image receiving sheet were
allowed to stand at room temperature for one day, and they were placed at
room temperature in such a manner that the heat sensitive ink and the
second image receiving layer came into contact with each other and passed
through a couple of heat rollers under conditions of 70.degree. C., 4.5
kg/cm.sup.2 and 2 m/sec. to form a composite. Temperatures of the sheets
when passed through the rollers were measured by a thermocouple. The
temperatures each were approx. 50.degree. C.
(4) Fixation of composite on image forming device
The above composite was cooled at room temperature for 10 minutes. Then,
the composite was wound around a rotating drum provided with a number of
suction holes in such a manner that the image receiving sheet was in
contact with a surface of the rotating drum, and the composite was fixed
on the rotating drum by sucking inside of the drum.
(5) Image recording
The laser beam (.lambda.:830 nm, out-put power:110 mW) was focused at a
beam diameter of 7 .mu.m on the surface of the light-heat conversion layer
of the composite to record a image (line), while, by rotating the drum,
the laser beam was moved in the direction (sub-scanning direction)
perpendicular to the rotating direction (main-scanning direction).
Main-scanning rate: 10 m/sec.
Sub-scanning pitch (Sub-scanning amount per one time): 5 .mu.m
(6) Formation of transferred image
The recorded composite was removed from the drum, and the heat sensitive
ink sheet was peeled off from the image receiving sheet by hand to obtain
the image receiving sheet having the transferred image (lines) of the heat
sensitive ink material wherein lines of magenta having width of 5.0 .mu.m
were formed in only the irradiation portion of the laser beam.
The resultant transferred image had a high concentration, no nonuniformity
of concentration and no image defect (existence of no image portion on the
image).
EXAMPLE 7
(1) Preparation of image receiving sheet
The same coating liquid for first image receiving layer as in Example 1 was
coated on a polyester film having fine pores therein (thickness: 100
.mu.m; trade name: Lumirror E60L, available from Toray industries, Inc.)
using a whirler, and dried for 2 minutes in an oven of 100.degree. C. to
form a first image receiving layer/thickness: 20 .mu.m) on the film.
Subsequently, the same coating liquid for second image receiving layer as
in Example 1 was coated on the first image receiving layer using a
whirler, and dried for 2 minutes in an oven of 100.degree. C. to form a
second image receiving layer (thickness: 2 .mu.m).
›Formation of image by laser beam and evaluation!
Using the above image receiving sheet and the same heat sensitive ink layer
as in Example 6, the procedures (3) to (6) in Example 6 were repeated to
form a transferred image on the image receiving sheet.
The resultant transferred image had a high concentration, no nonuniformity
of concentration and no image defect (existence of no image portion on the
image), which was the same as in Example 6.
Comparison Example 5
(1) Preparation of image receiving sheet
The procedures of Example 6 were repeated except for employing as the
plastic support of the image receiving sheet plastic support Clear
polyethylene terephthalate film having no pore (thickness; 100 .mu.m;
trade name: Rumiler #100, available from Toray Industries, inc.) to
prepare an image receiving sheet.
›Formation of image by laser beam and evaluation!
Using the above image receiving sheet and the same heat sensitive ink layer
as in Example 6, the procedures (3) to (6) in Example 6 were repeated to
form a transferred image on the image receiving sheet.
The resultant transferred image had a low concentration, nonuniformity of
concentration and some image defects (existence of no image portions on
the image) compared with in Example 6 or 7. Further, width of image line
of the transferred image was 4 .mu.m, which was lower than that of Example
6.
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